A washing brush to wash a container having a long length. The washing brush includes a handle part, a shaft part connected to the handle part, a sliding part configured to slide along the shaft part, a strip part coupled to the lower end part of the shaft part and lower part of the sliding part, a brush part attached to the outside of the strip part; and a position adjusting part configured to adjust a relative position of the shaft part. The sliding part is pressed to spread the strip part and the spread can be varied by the position adjusting part by adjusting the relative position of the sliding part with respect to the shaft part. A washing brush is provided that can simply and quickly wash a cylindrical container by allowing a washing part to be spread according to the shape of a container.