About 60% of patients with typical gastroesophageal reflux symptoms such as heartburn and regurgitation are considered to have non-erosive reflux disease (NERD). Patients with NERD show an overall poorer response to PPI treatment than patients with erosive reflux disease. Sodium alginate oral suspension is a medication indicated for the relief of gastroesophageal reflux symptoms. This multi-center, double blind, randomized trial aims to compare the efficacy and safety profiles of sodium alginate oral suspension (50 mg/ml) 20 ml three times daily with that of omeprazole (20 mg/capsule) 1 capsule once daily for the treatment of NERD patients in Taiwan. Efficacy assessments include percentage of patients achieving adequate relief of heartburn or regurgitation after 4 weeks treatment, improvement of reflux symptoms as assessed by reflux disease questionnaire before and after treatment, and patients overall satisfaction at the end of study. Safety assessments include incidence of adverse events and change of the laboratory test results. The study hypothesis is that treatment with sodium alginate is non-inferior to omeprazole in relieving heartburn or regurgitation symptoms of the NERD patients.