PURPOSE: To elevate cooling efficiency by a low noise, by detecting an abnormal temperature by each temperature sensor, controlling the rotational frequency of a cooling fan of an electronic computer in accordance with a result of its detection, and executing a cooling control of a module to be cooled, and the whole housing.

CONSTITUTION: Various mounting modules 2 of an electronic computer are stored in a housing 1, and in each module 2 and the housing 1, a fan assembly or fans 10, 3 are placed. Also, to both the module 2 and the fan 3, temperature sensors 4, 5 are fitted, respectively, and a temperature detected by each sensor 4, 5 is provided to an abnormal state detecting circuit 7. By this detecting circuit 7, an abnormal state of each module 2 and the fan 3 is detected, and in accordance with a result of its detection, a fan controlling circuit 6 is controlled. Also, by an output of the circuit 6, rotational frequency of the fan 3 for cooling the fan assembly 10 by each module 2, and the whole housing 1 is controlled, and the cooling effect is elevated by a low noise.