Mary Curnock Cook, who steps down at the end of April, suggests students may need down time after their finals.
Ms Curnock Cook told BBC Radio 4's Today programme that many youngsters needed time to find their career niche.
She urged students - and parents - not to feel stressed if they took time to find suitable employment.
"I'm not saying for a minute everyone should leave university and have a doss for a while," she told the BBC.
"But I do think it's unhelpful that universities' success in preparing people for graduate employment is measured by the number of people who are in graduate jobs after six months.
"Life, I don't think, works like that, it's not all about the lawyers, the medics and the people going into financial services.
"Lots of people need time to find their niche in the 21st Century workplace.
"If you've done a more generalist degree in let's say, economics or English or business or science, there's just a huge array of opportunities and career paths and it takes time for it all to come together."
Ms Curnock Cook, who is a parent, said students and their parents should not get too anxious if they move around between a number of jobs at the start of their careers.
"It's really unhelpful to make everyone get into a huge stress if they haven't landed a high-paying graduate job within six months - and that's what universities are measured on."
These days, she added, people could expect to have up to six or seven different career moves over their career lifetime, which gave them plenty of time to find their occupation and employment sector.
In an earlier interview with the Daily Telegraph, she said  there was no harm in doing temporary, voluntary or non-graduate work  before finding something more permanent.
Her comments follow concerns over whether universities are doing enough to promote students' mental wellbeing.
In September, the Higher Education Policy Institute urged institutions to review their mental health services and find out what could be improved.
Figures released by Ucas in February showed the number of would-be students applying for university had dropped for the third time in 15 years.
Around 30,000 fewer people had applied to start degree courses in autumn 2017 by 15 January - the main deadline for submitting applications.
Overall, 564,190 people applied to UK universities and colleges, down 5% (29,530 students) compared with the same point in 2016.
Ms Curnock Cook will be replaced in May by Clare Marchant, who is the currently the chief executive of Worcestershire County Council.
Students should not worry about finding a job while studying for their degree, says the outgoing head of university admissions service Ucas.