A power converting apparatus comprising: a first tensile force transmitting member configured to transmit a tensile force generated in response to a linear motion of a linear power source; an input shaft comprising a first power transmitting member configured to be connected to the first tensile force transmitting member and rotate; an energy transmitting shaft comprising a second power transmitting member configured to be connected to the first power transmitting member and perform a rotary motion; an energy storage unit configured to be connected to the second power transmitting member, store an elastic energy or a potential energy in response to a unidirectional rotation of the second power transmitting member, and rotate the energy transmitting shaft using the stored elastic energy or the potential energy when a linear force generated by the linear power source dissipates or decreases; an output shaft configured to rotate by receiving a torque alternately from the input shaft and the energy transmitting shaft; a first input device configured to transmit a torque of the input shaft to the output shaft; and a second input device configured to transmit a torque of the energy transmitting shaft to the output shaft; wherein the first power transmitting member is coupled to the input shaft through a first unidirectional rotation member configured to allow only a unidirectional rotation, and the second power transmitting member is coupled to the energy transmitting shaft through a second unidirectional rotation member configured to allow the same unidirectional rotation as the first unidirectional rotation member. a first tensile force transmitting member configured to transmit a tensile force generated in response to a linear motion of a linear power source; an input shaft comprising a first power transmitting member configured to be connected to the first tensile force transmitting member and rotate; an energy transmitting shaft comprising a second power transmitting member configured to be connected to the first power transmitting member and perform a rotary motion; an energy storage unit configured to be connected to the second power transmitting member, store an elastic energy or a potential energy in response to a unidirectional rotation of the second power transmitting member, and rotate the energy transmitting shaft using the stored elastic energy or the potential energy when a linear force generated by the linear power source dissipates or decreases; an output shaft configured to rotate by receiving a torque alternately from the input shaft and the energy transmitting shaft; a first input device configured to transmit a torque of the input shaft to the output shaft; and a second input device configured to transmit a torque of the energy transmitting shaft to the output shaft; wherein the first power transmitting member is coupled to the input shaft through a first unidirectional rotation member configured to allow only a unidirectional rotation, and the second power transmitting member is coupled to the energy transmitting shaft through a second unidirectional rotation member configured to allow the same unidirectional rotation as the first unidirectional rotation member.