PURPOSE: To detect a stopped fan out of a plurality of fans and, at the same time, to detect and display the connection defect of a cable in a fan-stop detection circuit.

CONSTITUTION: A fan-stop detection circuit is constituted of a fan-stop detector (1) 1, a fan-stop detector (2) and a fan-stop detector (n) 3 which are installed individually at a plurality of fans and which detect the stop of a fan, of an A/D converter 4 which detects the starting voltage Vx of a circuit, of a cable connection defect detection and fan-stop detection circuit 5 which detects the stop of a fan, of a CPU, for stopped-fan determing use, which determines a stopped fan and which discriminates a cable connection defect from the stop of a fan and of a CRT 7, for alarm display use, which displays a judged result.