To provide a dose distribution monitor capable of measuring a space distribution of a radiation with high precision.SOLUTION: A dose distribution monitor comprises a proportional counter tube 12 which has a plurality of detection channels (wire electrodes 22a-22c) for detecting a radiation, and a measuring circuit 13 which generates, based upon detected detection signals (amplified currents I1-I3), a dose space distribution which is a space distribution of the dose in radiation. The measuring circuit 13 comprises: a gas amplification factor computation part 50 which computes an electric field intensity E in the proportional counter tube 12, and computes, based upon the computed electric field intensity E and gas information stored in a gas information storage part 48, gas amplification factors M1-M3 for each of the detection channels； a correction computation part 43 which generates, based upon the detection signals by the detection channels and the gas amplification factors M1-M3, correction signals (after-correction currents Ia1-Ia3) by correcting the detection signals； and a distribution generation part 44 which generates a dose space distribution based upon the correction signals.SELECTED DRAWING: Figure 2【課題】放射線の空間分布を高精度に測定できる線量分布モニタを提供する。【解決手段】線量分布モニタは、放射線を検出する複数の検出チャネル（ワイヤ電極２２ａ～２２ｃ）を有する比例計数管１２と、検出された検出信号（増幅電流Ｉ１～Ｉ３）に基づいて放射線における線量の空間分布である線量空間分布を生成する計測回路１３を備える。計測回路１３は、比例計数管１２内の電界強度Ｅを演算し、この演算された電界強度Ｅと、ガス情報記憶部４８に記憶されたガス情報に基づいて、検出チャネル毎のガス増幅率Ｍ１～Ｍ３を演算するガス増幅率演算部５０と、検出チャネル毎の検出信号と、ガス増幅率Ｍ１～Ｍ３とに基づいて、検出信号を補正した補正信号（補正後電流Ｉａ１～Ｉａ３）を生成する補正演算部４３と、補正信号に基づいて線量空間分布を生成する分布生成部４４を備える。【選択図】図２
