To provide a washing brush capable of washing a substrate such as a semiconductor wafer evenly.

Projections 4 each with a contact surface 5 to be in contact with a substrate are mounted at regular intervals on the outer surrounding surface of a brush body 3 to be rotated. The projections 4 are formed on the outer surrounding surface of the brush body 3 with such an interval between each other that the contact area of the projections 4 along the peripheral direction of the brush body 3 with the substrate is nearly uniform in the axial direction when the brush body 3 is rotated.