A to-be-depressed member includes an elastic dome. A sectional shape of the dome orthogonal to an axis line (X2) of the dome is line-symmetric about a symmetry axis (Ax). The dome has a three-dimensional shape that is symmetric with respect to a virtual plane (Sx) containing the symmetry axis and the axis line. During a swinging movement responsive to a depressing operation, an opposed surface of an opposed member relatively approaches and contacts a distal end of the dome to deform the dome so as to generate a reactive force. As for an angle defined between the axis line of the dome and a normal line (X1) of the opposed surface, the angle (θ0) in an initial state falls in a range from a first angle variation amount from the initial state to a first-contact state to a second angle variation amount from the initial state to a depression-completed state.