A dose calculation device 50 includes: a detector 20 detecting a physical quantity as voltage; a V/I conversion element 28 converting the quantity into current; a memory 51 storing a zero point current and a shift amount from a true value caused by radiation; a correlation storage 52 storing zero point shift data in correlation between the zero point current and cumulative dose and span shift data in correlation between the cumulative dose and the shift; a first evaluator 53 estimating cumulative dose of the V/I conversion element 28 based on the zero point current and the zero point shift; a second evaluator 54 estimating cumulative dose of the V/I conversion element 28 based on the shift and the span shift; and a comparator 56 specifying a common cumulative dose as a true cumulative dose by comparing cumulative doses estimated by the first evaluator 53 and the second evaluator 54.