To time-sequentially measure an underground radiation dose at a specified point by using a commercially available survey meter.

An underground radiation dose measurement auxiliary tool 1 includes a cylindrical shielding main body 2, and a lateral opening 10 allowing the passage of a radiation is formed at the lower end part of the shielding main body 2. The lateral opening 10 is constituted of a slit extended in a circumferential direction or a through-hole isolated in the circumferential direction. An upper end insertion hole 6 for receiving a survey meter probe connected via a cable to, for example, an NaI scintillation type radiation dose measurement unit (survey meter) is disposed on the upper end face of the shielding main body 2. The underground radiation dose measurement auxiliary tool 1 into which a probe P has been inserted is inserted into an underground vertical hole 18 to record a radiation dose at a desired depth position.