Abstract: A bag sealer that can vacuum or inflate the plastic bags to be sealed. It is especially for domestic use. This bag sealer comprises the body, top cover the nozzle located a little behind on the body, pipe circuit for airflow, the mechanism to vacuum and inflate, the switch to alternate the said dual functions. The mechanism can be of propeller type or piston pump type. When a propeller is used, there is one pipe for airflow. The directions of the airflow is caused by whether the propeller is turned clockwise or anticlockwise by the motor driven by the switch set to either the negative or positive polarity of the power supply. When a piston pump is used, the pipe circuit has one pipe for air intake therefore to vacuum the bags, and one for air outflow hence to inflate the bags. The main benefit is that the bag sealer has dual functions; consumers need only to turn a switch to alternate the functions.