An auxiliary tool to be detachably attached to tip portions (36, 46) of a pair of arms (30, 40) which are opened/closed by each rotating relative to a base (24) of an actuation device (e.g., hydraulic actuation device (10)), includes a first auxiliary member (60) to be detachably attached to a first arm (30) of the pair of arms (30, 40), the first auxiliary member (60) having at least one claw portion (62), and a second auxiliary member (70) to be detachably attached to a second arm (40) of the pair of arms (30, 40), the second auxiliary member (70) having at least one claw portion (72). Positions of the claw portion (62) of the first auxiliary member (60) and the claw portion (72) of the second auxiliary member (70) are such positions that the claw portion (62) of the first auxiliary member (60) and the claw portion (72) of the second auxiliary member (70) do not come into contact with each other even when the arms (30, 40) are closed in a state in which the first auxiliary member (60) is attached to the first arm (30) and the second auxiliary member (70) is attached to the second arm (40).