An energy-storing unit with a forcing mechanism and an on-load tap changing device provided with the same which employ an inexpensive and simple structure and which can suppress a loading torque to operate stably. A forcing mechanism built in an energy-storing unit includes a protrusion, a bearing, and a loading cam. Among those components, the protrusion is attached to the bottom face of an eccentric cam, and the bearing is attached to the tip of the protrusion. The loading cam is an isosceles triangle having a vertex that is substantially 90 degrees, and is attached to the top face of an energy-storing case. The loading cam becoming in contact with the bearing causes a crank to rotate through the energy-storing case, and feeds a catch to a standby position.