An animal experiment apparatus is disclosed. Heated air or cooled air introduced into an air fan chamber provided in a housing is circulated in the housing by an air fan. The housing is vertically divided into a plurality of chambers by reticulate partition shelves and a cage containing a small animal is put into and out of each chamber. The housing is provided with a commutator plate for controlling the circulating air and/or a temperature detector, a humidity detector, a control unit for controlling the housing in accordance with signals from the detectors, and a brightness-controlling device.