An end effector (4) comprises an end effector base (5) connected to a robot arm and an elastic component holding means (9) provided to the end effector base (5) and for holding an elastic component (O2). The elastic component holding means (9) comprise a plurality of elastic component gripping members (12) for gripping an elastic component (O2) in a releasable manner; and a biasing means (14) for elastically biasing the tip of each of the plurality of elastic component gripping members (12) from a release position in which the elastic component (O2) is released toward a grip position in which the elastic component (O2) is gripped. Thus provided is an end effector that simplifies the fitting of an elastic member such as an O-ring.