According to an operation of a shift lever to parking range, a cam member at a parking rod comes in between a parking pole and a support member, and the parking pole swings so that a pawl portion of the parking rod can engage with a parking gear. A concave holding portion to hold the support member is formed at a transmission case. The support member comprises a first cylindrical outer face having a first radius R1 which is supported in a concave inner face the concave holding portion to rotate in a specified range and a second cylindrical outer face (cam-contact portion) having a second radius R2 which contacts a cam member. The first radius R1 has a center which is located at the same position as that of the second radius R2. Herein, R2 is shorter than R1.