A machining device comprises a fixed base, a sliding assembly arranged in the fixed base, a machining assembly arranged on the sliding assembly and a braking mechanism arranged in the fixed base. The machining assembly can move relative to the fixed base under the drive effect of the sliding assembly; the braking mechanism comprises a rack, an installation part, a base, resetting parts, a braking part and an elastic part, the rack is fixed to the sliding assembly, the installation part is fixed to the rack, the base is arranged on the installation part or the braking part in a sliding mode and is provided with an orienting part, the two ends of each resetting part abut against the base and the installation part respectively, the braking part is movably arranged on the installation part and comprises guiding parts and meshing parts fixed to the guiding parts, the guiding parts and the orienting parts are matched in a sliding mode, the elastic part is arranged between the base and the braking part, and the elastic part and the resetting parts are located on the two sides of the braking part respectively. According to the machining device, the machining assembly and the sliding assembly can be effectively prevented from moving continuously under the inertia effect on the power down occasion.