Antony Ricketts, 20, was also ordered to pay costs of £186.31 after being convicted in his absence in Carmarthen.
He was also found guilty of putting non-recyclable waste out in blue bags in Barnsfield Terrace.
"Bags of rubbish left littering the streets for days on end will not be tolerated," said Councillor Jim Jones, environment executive member.
Ricketts must also pay a victim surcharge of £20 after the conviction under the Environmental Protection Act.
Ricketts was warned by council officers, but problems continued and they found evidence linking him to black bags and contaminated blue recycling bags on several occasions.
Two people from Llanelli have already been fined £100 after Carmarthenshire Council announced it was getting tough with householders who put out waste on the wrong day.
Mr Jones added: "If a resident continually ignores the council's advice we have no choice but to issue a fine or prosecute them in court.
"I hope residents take notice of this case and act responsibly to reduce the amount of rubbish littering our streets."
A man who continually put his rubbish out on the wrong day has been fined £200 by magistrates.