An applicator (100) for applying a treatment agent to one's hair includes a container connector (110) for connection with a dispensing container (ST) accommodating therein the treatment agent, an upper guide member (120) formed in a hollow shape so as to extend forward from the container connector (110) and including an outlet formed in a lower face for dispensing the treatment agent, a lower guide member (130) disposed parallel to the upper guide member so as to oppose the outlet, and a parallel supporting body (140) that displaces at least one of the upper guide member (120) and the lower guide member (130) up and downward, while maintaining the guide members parallel to each other. With the applicator (100) an individual user can easily apply the treatment agent uniformly to the hair.