Abstract: A mechanical disc brake includes a caliper floatingly supported on a stationary member, and a force converting mechanism mounted on the caliper and comprising a rotatable member rotatable in response to a rotary input force, an inclined surface formed on one side of the rotatable member, a ramp member disposed adjacent to the rotatable member with an inclined surface formed thereon for cooperating with the inclined surface of the rotatable member, and at least one ball member interposed between the inclined surfaces for reducing frictional resistance in converting the rotary input force into a linear output force. A dust cover is disposed to cover the ball and the inclined surfaces and has a first end mounted on the rotatable member and a second end mounted on the ramp member.