PROBLEM TO BE SOLVED: To provide a work machine that switches a power transmission mechanism transmitting power to a travelling unit to a neutral state to stop a travelling machine body by detecting an obstacle with a contact-type obstacle sensor but can smoothly switch the power transmission mechanism to the neutral state.SOLUTION: In the work machine, the obstacle sensor 70 is configured to permit the moving operation thereof on an opposite side of an undetectable position N exceeding a detectable position T by coming into contact with an obstacle.COPYRIGHT: (C)2015,JPO&INPIT