The present invention discloses a shading device includes a screen, a shaft portion having a lock portion to be locked, a biasing mechanism, a locking member that is engaged at a lock position with the lock portion, and a housing in which the end portion of the shaft portion is inserted. The housing has a sliding guide portion in which the locking member is slid. The sliding guide portion is capable of guiding the locking member in a direction passing through the lock position and a lock release position, and has a lock position engagement portion for stopping the locking member from sliding at the lock position. The locking member includes a slide engagement portion that engages with the lock position engagement portion at the lock position and an operating portion that can be flexed to release the slide engagement portion from the lock position engagement portion.