A knee-action-type suspension comprising: an arm member which is pivotable in upward and downward directions about a pivot supported on a vehicle body; a lower spring seat which is provided on the arm member; an upper spring seat which is disposed above the lower spring seat; and a compression coil spring which is arranged between the lower spring seat and the upper spring seat, and urges the arm member downward in a compressed state, a wire of the compression coil spring comprising: a large-diameter wire portion which is arranged on a side near to the pivot, and has a wire diameter which is greater than an average wire diameter of the wire; a small-diameter wire portion which is arranged on a side far from the pivot, and has a wire diameter which is smaller than the wire diameter of the large-diameter wire portion; a wire diameter varying portion whose wire diameter is continuously varied between the large-diameter wire portion and the small-diameter wire portion characterized by a lower-end-side end turn portion which contacts an upper surface of the lower spring seat, a wire diameter of the lower-end-side end turn portion being smaller than the wire diameter of the small-diameter wire portion; and an upper-end-side end turn portion which contacts a lower surface of the upper spring seat, a wire diameter of the upper-end-side end turn portion being smaller than the wire diameter of the small-diameter wire portion. an arm member which is pivotable in upward and downward directions about a pivot supported on a vehicle body; a lower spring seat which is provided on the arm member; an upper spring seat which is disposed above the lower spring seat; and a compression coil spring which is arranged between the lower spring seat and the upper spring seat, and urges the arm member downward in a compressed state, a wire of the compression coil spring comprising: a large-diameter wire portion which is arranged on a side near to the pivot, and has a wire diameter which is greater than an average wire diameter of the wire; a small-diameter wire portion which is arranged on a side far from the pivot, and has a wire diameter which is smaller than the wire diameter of the large-diameter wire portion; a wire diameter varying portion whose wire diameter is continuously varied between the large-diameter wire portion and the small-diameter wire portion characterized by a lower-end-side end turn portion which contacts an upper surface of the lower spring seat, a wire diameter of the lower-end-side end turn portion being smaller than the wire diameter of the small-diameter wire portion; and an upper-end-side end turn portion which contacts a lower surface of the upper spring seat, a wire diameter of the upper-end-side end turn portion being smaller than the wire diameter of the small-diameter wire portion. a large-diameter wire portion which is arranged on a side near to the pivot, and has a wire diameter which is greater than an average wire diameter of the wire; a small-diameter wire portion which is arranged on a side far from the pivot, and has a wire diameter which is smaller than the wire diameter of the large-diameter wire portion; a wire diameter varying portion whose wire diameter is continuously varied between the large-diameter wire portion and the small-diameter wire portion characterized by a lower-end-side end turn portion which contacts an upper surface of the lower spring seat, a wire diameter of the lower-end-side end turn portion being smaller than the wire diameter of the small-diameter wire portion; and an upper-end-side end turn portion which contacts a lower surface of the upper spring seat, a wire diameter of the upper-end-side end turn portion being smaller than the wire diameter of the small-diameter wire portion.