PROBLEM TO BE SOLVED: To provide a motor-driven braking device having an electric motor and its driving circuit on the wheel side, capable of improving the reliability of electronic components including the driving circuit against the vibration of a vehicle when travelling.SOLUTION: To a mount member MTB fixed to a supporting member supporting a wheel, first and second guide members GD1, GD2 are fixed in parallel to each other. A caliper CPR is supported to be relatively movable in the axial direction by the first and second guide members GD1, GD2. An electric motor MTR is fixed to the caliper CPR. Switching elements S1-S4 for controlling the electric motor MTR, an inductor IND, and capacitors CND1, CND2 are built in the caliper CPR, and located inside a guide quadrangle (Mgd) in view from the vertical direction with respect to the flat surface of the guide quadrangle (Mgd, quadrangle A-B-D-C) of which four corners are at both end points A, B of the first guide member GD1 and at both end points C, D of the second guide member GD2.