The invention belongs to the field of clothes washing equipment, particularly provides a positioning device for a roller of a washing machine and the roller washing machine and aims at solving the problem that the positioning precision of a roller of a washing machine is poor due to the fact that a positioning point of the roller of the washing machine cannot be precisely detected in the prior art. For the purpose, the positioning device for the roller of the washing machine comprises a light signal transmitter, a light signal receiver and a light hole formed in a belt wheel of the washing machine. The light signal transmitter and the light signal receiver are separately arranged on the two sides of the light hole, and only when the light hole rotates around the axis of the belt wheel to the position where the light hole is aligned with both the light signal transmitter and the light signal receiver, the light signal receiver can receive light signals transmitted by the light signal transmitter. Thus, when a roller door of the positioning device is positioned, the positioning point is more easily and precisely detected, and the positioning precision of the roller of the washing machine is improved accordingly.