The invention discloses a mechanical device for washing workpieces. The mechanical device comprises a movable base, a clamping device, the workpieces, a fixing support, a first motor, a rotary base, an oil cylinder, a first overturning base, a first connecting piece, a first washing motor, a connecting base, an overturning motor, a second overturning base, a second washing motor, a second connecting piece, a washing tank, a washing spray head, a washing brush and a sewage drainage pipeline. The mechanical device has the beneficial effects of being reasonable and simple in structure, low in production cost and convenient to install and has complete functions. The mechanical device is provided with two clamping stations, one clamping station carries out washing while the other station carries out workpiece clamping, the arranged overturning motor can effectively overturn the two clamping stations, and therefore the workpiece can be washed and clamped conveniently; and the arranged first motor can enable the two clamping stations to exchange, the arranged oil cylinder can enable the workpiece to be moved to the washing tank to be washed while needing to be washed, and therefore the working environment of washing is improved.