A chin guard positioning assembly connects a helmet body and a chin guard to each other. The helmet body provides a certain space to allow a user's head to be inserted thereinto and the position of the chin guard is allowed to be moved from a protective position to an open position. The chin guard positioning assembly includes a movable base part in which a position thereof is moved together with the chin guard. A fixed base part is connected to the helmet body and connected to the movable base part to serve as a reference for the movement of the position of the movable base part. A fixed magnetic force part is fixed to the fixed base part. A movable magnetic force part is fixed to the movable base part to fix the movable base part to a first position or a second position.