To provide a tool and method for press-fitting a weather strip by a continuous motion along the weather strip.

A handle 35 is extended at a proper angle from the top part of a tool head, and its grip part can be swung about the longitudinal axis of the handle. Also the tool head can trace the flange at the opening part of a door by guiding the motion of the tool head through the outer surface of a door flange. When the arm motion of an operator is advanced, the handle 35 to be swung can adopt to an angle variation. In addition, a press-fitting roller pressed against a spring is installed pivotally to the tool head opposedly to a fixed type press-fitting roller. Both press-fitting rollers are driven by power, and a clearance between the axis of the press-fitting roller and both press-fitting rollers can be varied according to the advancement of the operation of the tool. Thus the rollers can adopt to a variation in thickness of the flange at the opening of the door.