To improve the working property by arranging one of beads of a tire on a rim and on the side surface of the other sheet, axially moving and inserting the first bead into a groove, mounting the other bead on a second seat, pulling out the first bead from the groove, and then mounting it on a first seat.

In mounting a tire 20 on a rim 30, the first bead 21 of the tire 30 is arranged within the groove 34 of the rim 30, and the other bead is fitted to a second seat. A finger 13 is energized in this state to add a force to the side wall 24 of the tire 20, whereby a local space is formed between the bead 21 and the inside flange of the first seat 32, and during this, an arm 14a is pivotally moved in direction B on a first pivotal pin 16 to insert a grip means 14 to the local space. The addition of the force to the side wall 24 is then stopped, the center part of the grip means 14 is made to abut with the inner surface 21a of the bead 21 in the middle pulling-out position, and a control means 15 is then pivotally moved in direction C around a pin 18 to pull out the grip means 14.