Provided are an adaptor for assembling a wiper blade, a wiper blade assembly, and a wiper device. The adaptor for assembling a wiper blade, which is configured to couple the wiper blade to two or more types of wiper arms, includes a body portion coupled to the wiper blade and to which a first type wiper arm is coupled horizontally or to which a second type wiper arm is coupled vertically and a locking portion rotatable provided on the body portion to cover a front end of the wiper arm.