To provide a body worn booster having high maneuverability which enables a personnel such as a care-giver to exert a stronger power than one's muscle strength and to perform physical labors efficiently without using a huge apparatus and which thereby can alleviate the backache of the care-giver.

An actuator wearing mechanism 1 installed with a wire winding drum 3 as an actuator is worn detachably on the buttock of a user. A booster transmitting mechanism 11 worn detachably on the upper body of the user is pivoted rotatably in the backward and forward direction on the upper side of the actuator wearing mechanism 1, and a reaction receiving mechanism 31 that cooperates with the movement of the lower limbs of the user is provided on the downside of the actuator wearing mechanism 1. A booster transmitting wire 24 is stretched between the actuator of the actuator wearing mechanism 1 and the booster transmitting mechanism 11, and a tension transmitting wire 38 is stretched between the actuator wearing mechanism 1 and the reaction receiving mechanism 31.