Ventilation regulated hot air supplied constant temperature oven

A ventilation regulated hot air supplied constant temperature oven wherein heated air of a predetermined temperature is supplied to a test oven body provided with an air supply port and an air discharge port with the ventilation of said test oven carried out at a predetermined rate at predetermined time intervals, comprising an oven body having an air supply port and an air discharge port to which a discharge cylinder is joined, a blower connected to said air supply port via an air supply passage, a differential pressure detector connected to said discharge cylinder and adapted to detect a differential pressure corresponding to the air flow rate on the basis of the data obtained in advance on the relation between a difference between the pressure at an outlet port of said blower and that at said discharge cylinder and the air flow rate, and a blower's revolutions regulator provided between said blower and said differential pressure detector and adapted to control the number of revolutions per minute of said blower in accordance with an output level of a signal corresponding to a differential pressure measured with said differential pressure detector.