To provide a vertical installation assisting tool easily fitted to an intermediate part of a bolt body to which a support of a supported body is fitted, to assist for the vertically installed state of the bolt body.

One end side of an assisting tool body 2 is provided with an engaging part 3 engaged with the bolt body 21, and the other end side of the assisting tool body 2 is provided with a fixed part 4 fixed to a foundation floor face. The engaging part 3 is provided to juxtapose an upper piece 7 and a lower piece 9 at a predetermined space in the axial direction of the bolt body 21 in the engaged state with the bolt body 21 to form a cutout opening 5 and an engaging space 6 in which the bolt body 21 is disposed. The cutout opening 5 is formed to allow the bolt body 21 to move from the side and to be inserted into the engaging space 6 from a clearance between the upper piece 7 and the lower piece 9. The engaging space 6 is formed to allow the upper piece 7, the lower piece 9 and a connecting piece 11 to abut on the outer peripheral surface of the bolt body 21 at the respective end faces from mutually different directions by bringing the other end side of the engaging space 6 close to the bolt body 21 in the state of disposing the bolt body 21 inside.