To eliminate the cause of a lowering of power transmission efficiency due to continuous leakage of a hydraulic fluid by constituting so as to hold a neutal state by forming an orifice hole for communicating a main circuit with a charge circuit in a check valve cartridge in a new HST type transmission.

A pair of check valves 35 are integrally housed in a single sleeve 38, the check valve cartridge C is constituted, and is slidingly installed on an oil passage plate 32, neutral coil springs 41 for energizing the check valve cartridge C to the intermediate position side are arranged on both sides, an orifice hole 38d for communicating the main circuit 32m with the charge circuit 32c is formed in the check valve cartridge C, and only when the check valve cartridge C is positioned in the vicinity of an intermediate position, the main circuit 32m is communicated with the charge circuit 32c by the orifice hole 38d.