Fan control device and fan control method

A fan control device that controls a fan used for cooling a cooling target in a vehicle, the fan control device comprising:

• a memory storing instructions;
• and
• a processor that implements the instructions to
• acquire an environmental sound in the vehicle collected by a microphone provided in the vehicle;
• derive first analysis data by executing frequency analysis on the acquired environmental sound;
• acquire second analysis data obtained by executing frequency analysis on a fan sound that varies depending on a rotation speed of the fan and that is a sound generated during rotation of the fan;
• and
• determine an upper limit of the rotation speed of the fan based on the first analysis data and the second analysis data such that a first index of the environmental sound satisfies a predetermined first condition, the first index being an index related to audibility.