A dose rate monitoring device contains a first radiation detector including an inorganic crystal scintillator, a second radiation detector including a plastic scintillator, a detector mount having a cylinder part, a low range calculator calculating a first compensation dose rate of an incident radioactive ray based on the detection signal pulse, a high range calculator calculating a second compensation dose rate of an incident radioactive ray based on the detection signal pulse, a dose rate calculator calculating a dose rate ratio from the first compensation dose rate and the second compensation dose rate, and choosing a compensation dose rate according to the magnitude of the calculated dose rate ratio; and a display displaying the compensation dose rate which is outputted from the dose rate calculator, wherein the plastic scintillator which is included in the second radiation detector is wound around the cylinder part of the detector mount.