PURPOSE: To prevent the leakage of the transmission oil to an area for storing the brake fluid by arranging a hydraulic auxiliary piston on a shaft different from a shaft of a stem and in parallel with the stem shaft, and connecting this hydraulic auxiliary piston to the stem through a mechanical transmission.

CONSTITUTION: A hydraulic piston 16 is arranged on a shaft 18 different from a shaft 19 of a stem 17 of an inching valve and in parallel with the shaft 19, and connected to the stem 17 through a mechanical transmission 21 freely to be operated. When the inching valve is positioned at the mounting position, the hydraulic piston 6 is arranged on the shaft 19 of the stem 17, and the hydraulic piston 16 has a rod 20 projected from a valve main body, and connected to an auxiliary piston 22 by a rigid connecting member 21. The auxiliary piston 22 is connected to the stem 7 freely to be operated, and arranged as an extension part of the shaft 19.