PURPOSE: To obtain a β-ray tissue dose equivalence ratio ionization chamber type surveymeter wherein it is possible to read directly with high accuracy a predetermined nuclear kind β ray 70 micrometer dose equivalence ratio with out using a calibration table.

CONSTITUTION: In a surveymeter 30, a double graduations indication meter 36 is arranged. There are formed, in an indication plate, a first scale portion 39 which is positioned at a top edge side of a needle 38 and has a scale range from 0 to 1.0, and a second scale portion (an enlarged magnification scale) 40 which is adjacent to an inside against this scale portion and has a scale range from 0 to 1.5. The second scale portion 40 has a scale of 1.5 times as large as that of the first one. Against a ray source nuclear kind which is at a higher energy side than 137Cs, the first scale portion 39 is used, and against a ray source nuclear kind which is at a lower energy side than 60Co, the second scale portion 40 is used. By this 1.5 times scale portion 40, a decrease in an indication error is achieved.