CONSTRUCTION MACHINE

A construction machine includes: a negative parking brake (4) whose braking state is released by supply of hydraulic fluid; and a parking brake hydraulic circuit (5) that is branched from a hydraulic fluid supplying circuit (6) supplying the hydraulic fluid to a transmission of the construction machine and supplies the hydraulic fluid to the parking brake (4). The parking brake hydraulic circuit (5) includes: a check valve (72) that prevents backflow of the hydraulic fluid of the parking brake (4) to the hydraulic fluid supplying circuit (6); an operation switching valve (71) that is provided closer to the parking brake (4) than the check valve (72) and switches between an activation and a release of the parking brake (4); and a relief valve (73) that is interposed between the check valve (72) and the operation switching valve (71) and discharges the hydraulic fluid of the parking brake (4) when the relief valve (73) is opened.