PROBLEM TO BE SOLVED: To provide a controller for a ventilation blower which can control the indoor temperature so that it is within a desired temperature range.SOLUTION: A controller for a ventilation blower includes a detection unit 102 detecting the outdoor temperature &thetas;, and a control unit 106 which determines whether or not the outdoor temperature &thetas; is between a first temperature A1 and a second temperature A2, and controls a ventilation system for ventilation between the outdoor and the indoor on the basis of the determination result.