Abstract: An adjustable handle auxiliary device includes a main handle body, a handle, a resting part, a tank body and at least one clamping part. The main handle body has one side having a docking portion, and one end edge having a combination tooth portion. The handle has a combination portion. The combination portion and the docking portion can be mutually combined together. The resting part has one side having a resting slot and the other side having a toothed combination slot. The toothed combination slot and the combination tooth portion can be mutually combined together. The tank body is formed with a chamber. The main handle body is disposed in the chamber. The tank body is provided with multiple jointing members. The clamping part includes a first clamping member, a second clamping member and a third clamping member combined together. The second and third clamping members clamp the jointing members.