A beverage dispenser (1) includes a cold water tank (20) for storing cold water (50), a carbonation tank (30) disposed with at least a bottom portion thereof being submerged in the cold water (50) in the cold water thank (20), the carbonation tank being configured to generate carbonated water (60) by adding carbon dioxide gas to the cold water (50) supplied from the cold water tank (20), a carbonated water outlet passage (35) for taking out the carbonated water (60) from the carbonation tank (30) and a heater (41) for heating the cold water (50) in the cold water tank (20). In order to sterilize the above beverage dispenser (1), the heater (41) is caused to heat the cold water (50) in the cold water tank (20) to a temperature higher than a predetermined temperature, thereby to sterilize the cold water tank (20) and the carbonation tank (30). After the carbonated water (60) in the carbonation tank (30) is taken out via the carbonated water outlet passage (35), hot/warm water (70) in the cold water tank (20) is cooled.
