Servo driver with simple assembly work of capacitor to housing

A servo driver for controlling an operation of a servo motor, comprising:

• a capacitor that constitutes a smoothing circuit of an inverter and has a substantially cylindrical outer shape;
• a case body in which the capacitor is stored;
• and
• a housing that houses the capacitor and the case body,
• wherein the case body has a substantially box-like shape formed by being provided with an opening portion that makes it possible to take in and out the capacitor with respect to the case body along a direction orthogonal to an axial direction of the capacitor,
• wherein the case body is assembled to the housing so that the opening portion is covered with a closing portion that is a part of the housing, and
• wherein the capacitor is sandwiched and held between the closing portion and a bottom portion of the case body located on a side opposite to a side on which the opening portion is provided while being elastically biased to the bottom portion with a cushion material that is elastically deformable and is interposed between the closing portion and the capacitor.