Washout processor and washing method

A washout processor that develops an imagewise exposed flexographic printing plate precursor using a washing solution with a developing brush, the washout processor comprising:

• a development unit that performs development using the washing solution by simultaneously performing circular movement and linear reciprocation of the developing brush on the imagewise exposed flexographic printing plate precursor,
• wherein the circular movement and the linear reciprocation of the developing brush by the development unit satisfy, of the following conditions (a) to (c), at least conditions (a) and (b) or conditions (b) and (c),
• condition (a) in a case where a stop time in a case of switching between directions of the linear reciprocation of the developing brush is t seconds and a rotation speed of the circular movement of the developing brush is R times per second, t<R,
• condition (b) in a case where the number of times of linear reciprocation per unit time in the linear reciprocation of the developing brush is f times per second and the rotation speed of the circular movement of the developing brush is R times per second, f<R,
• condition (c) in a case where a moving distance in the linear reciprocation of the developing brush is d millimeters and a radius of the circular movement of the developing brush is r millimeters, d≥r.