Abstract: An anti-icing system at least includes: a precooler that exchanges heat between bleed air and outside air; and an anti-icing unit that receives the bleed air passed through the precooler. A bleed air flow rate adjusting section that adjusts a flow rate of the bleed air supplied to the anti-icing unit adjusts the flow rate of the bleed air to suppress pressure of the bleed air to a pressure upper limit or lower by using relationship r1 and relationship r2. The relationship r1 is a relationship between an altitude and a pressure upper limit of the bleed air. The relationship r2 is a relationship between the pressure upper limit and outside air temperature at which the temperature of the bleed air reaches allowable temperature of ducts and other members through which the bleed air flows. The relationship r2 is provided based on the altitude.