A wearable apparatus for assisting muscular strength includes: a main body mechanism extending in a vertical direction of a wearer's torso, and being fixed to a side of a wearer's torso under a wearer's shoulder; a fastening mechanism extending along an extension direction of a wearer's upper arm, and being disposed at and being in contact with a lower surface of the wearer's upper arm; a connecting mechanism having a first end coupled to the fastening mechanism and a second end movably coupled to the main body mechanism so as to be movable with respect to the main body mechanism; and a support mechanism movably coupled between the first end and the second end of the connecting mechanism to apply a support force to the connecting mechanism, and coupled to the main body mechanism and movable with respect thereto.