An excavating tool includes a casing pipe that forms a cylindrical shape about an axis line and in which a stepped portion whose inner diameter is decreased by one step is formed in an inner peripheral portion of an distal end; an inner bit where a contact portion which can come into contact with the stepped portion is formed in an outer periphery, which is inserted into the casing pipe, and whose distal end portion protrudes from a distal end of the casing pipe; an engagement convex portion that is disposed on the outer periphery of the distal end portion of the inner bit so as to be retractable; a ring bit that forms an annular shape and is arranged around the distal end portion of the inner bit; and an engagement concave portion that is formed in an inner peripheral portion of the ring bit.