A circuit-board holder includes a first restraint, a second restraint, and a third restraint. The first restraint restricts a circuit board from moving in a direction orthogonal to an insertion direction of the circuit board. The circuit board is inserted to the circuit-board holder in a direction parallel to a surface of the circuit board. The second restraint restricts the circuit board from moving in a normal-line direction to the surface of the circuit board. The third restraint restricts the circuit board from moving in the insertion direction of the circuit board when the circuit board has been inserted to a prescribed position. One end of the third restraint in the insertion direction of the circuit board is fixed. Another end of the third restraint in the insertion direction of the circuit board is elastically deformable and displaceable in a normal-line direction to the surface of the circuit board.