One object of the present invention is to provide a self-inking stamp which can easily perform replacement of a character arrangement block or an ink pad without sudden release of locked condition of the stamp during the replacement operation. According to the present invention there is provided a self-inking stamp comprising an inner frame member (10) provided therein with a reversing guide (14), an outer frame member (20) slidably mounted on the inner frame member (10) via an elastic member or members (30) therebetween, a main body (50) of stamp containing the character arrangement block (51) and adapted to be reversed by the reversing guide (14), and an ink pad (42) adapted to be arranged within the inner frame member (10) characterized in that the inner frame member (10) is formed on its side wall with a projection (16) movable toward the inside of the inner frame member (10), that the outer frame member (20) is formed on its side wall a pusher (26) for pushing the projection (16) toward the inside of the inner frame member (10) and an engaging portion (27) adapted to be engaged with the projection (16), and that a vertical relative motion between the inner and outer members (10, 20) is locked when the projection (16) is fitted in the engaging portion (27) and the lock is released when the pusher (26) is pushed inside to disengaging the projection (16) from the engaging portion (27).