The proposed is directed to a shampoo assisting device that is mounted on a wash basin, a bathtub, a sink, etc. with a simple configuration to allow the user to be shampooed while lying down. The shampoo assisting device includes a main body having a locking part provided on one side and a headrest part provided on the other side to support a user's head, and a first support protruding from a lower portion of the main body so as to be closely supported by a bottom surface of a wash basin.