To provide a drain system for a torque converter preventing oil drainage from the torque converter during a state in which an engine is stopped.

A drain system for a torque converter amplifying torque of an engine by using oil supplied from a hydraulic pump operated by torque of the engine and transmitting the amplified torque of the engine to an input shaft of a transmission, comprises: a drain flow path formed so that oil used in the torque converter is drained to the transmission therethrough; a control flow path adapted to transmit the oil discharged out of the hydraulic pump to the drain flow path; and a switch valve disposed at the drain flow path and adapted to operate by pressure of the oil supplied through the control flow path. The switch valve selectively opens or closes the drain flow path.