Abstract: A breathing apparatus adapted for use in combination with a tube for swimming, the breathing apparatus includes a floatable body having a hollow case for floating over water level and an opening; and a breathing assembly mounted detachably. The breathing assembly has a connector inserted within the opening of the floatable body; a fixing cap mounted on the floatable body for preventing separation of the breathing assembly from the floatable body, and for providing fresh air from the outside to the breathing assembly; a mouth connecting member connected to the connector and providing air to the swimmer's mouth; an air intake check member having an inlet check valve opened only in one direction for preventing upward flow of exhausted air; and a water intake check member having an outlet check valve also opened only in one direction for discharging exhausted air and for preventing entry of water into the breathing assembly.