To enable one person to surely measure vertical interval, shorten measurement time, and also achieve simplification of marking work and the reduction of working hours.

This vertical interval measuring instrument is equipped with a measurement ruler 11, a level 21, a reference irradiation light detecting means 31, and a scale part 41. The measurement ruler 11 is provided with an erecting assist part 51. The assist part 51 has a leg part 52, with its base end part fixed to the ruler 11 and its front end part projecting away from the ruler 11, and a treadle part 56 provided on the front end part of the leg part 52. When the treadle part 56 is stepped by feet of a worker and pressed against a measurement surface (floor face FL), the ruler 11 can be assisted in being held in the erect state. Further, the leg part 52 of the assist part 51 is adapted so that the front end part is positioned below the base end part, when the ruler 11 is in its erect state, and the length of the leg part 52 is constituted to be adjustable, when the treadle part 56 is treaded by the worker's feet and pressed against the measurement surface (FL).