A Pentamethylene diisocyanate is obtained by phosgenating pentamethylenediamine or its salt obtained by a biochemical method, and contains 5 to 400 ppm of a compound represented by the general formula below and a compound represented by the general formula below in total:. A compensation circuit may include a compensation comparator for comparing the comparison signal generated using the output signal of a comparator, to a reference voltage. T2’s emitter is connected to T3’s collecter.