The present disclosure provides an axle device and a boring tool. The axle device includes a main shaft, an expanding unit, a drill, and an engaging unit. The main shaft is magnetic. The expanding unit includes a cone blocking member and an expanding member. The cone blocking member has an inclined plane. The expanding member is limited at the main shaft and includes a plurality of pawls, wherein the pawls are against the inclined plane. The engaging unit includes a rotating member and an engaging element. The rotating member is screwed on the main shaft. The engaging element engages the drill with the rotating member. When the rotating member rotates and moves toward a first direction, the engaging element correspondingly brings the drill and the cone blocking member toward the first direction, such that the inclined plane of the cone blocking member expands the pawls outwardly.