To provide a ground stress measuring device and a ground stress measuring method capable of protecting a load cell or the like from getting wet with water and detecting each strain (stress) of a structure.

A tunnel model ground stress measuring device 101 comprises a load cell 10 having a base section 11 attached with a perpendicular strain gauge 15 and a shearing strain gauge 16 and an inside pressure plate 13, a rubber film 61 arranged outside the inside pressure plate 13, an outside pressure plate 20 that is arranged outside the rubber film 61 at an arrangement place of the inside pressure plate 13 and is fixed to the inside pressure plate 13 with a joint screw 50, and a sealing material or sealing agent that is arranged in a clearance or the like around the joint screw 50 and prevents water or the like of external model ground 301 from intruding into a space V1 in the rubber film.