To smoothly mark a clear and hardly erasable line and save on labor.

An endless flexible member following the lower outer periphery of a lower roller 44 on a line marking part 4 comes into contact with the upper face of a platen 2, and the lower roller 44 is rotated by moving an entire caster case 43 under such a state. Further, the endless flexible member following the outer periphery runs on the platen 2, changing its contact areas with the platen 2 one after another. In this case, a paint for making a line which sticks to the endless flexible member in the caster case 43 comes out of the caster case with the endless flexible member and then is transferred to the platen 2 when the endless flexible member comes into contact with the platen 2. Thus a line is marked on the platen 2.