An anti-icing system of an aircraft, the anti-icing system preventing, in operation, icing on the aircraft with use of bleed air heat-exchanged with outside air, the anti-icing system comprising: a heat exchanger that is arranged to exchange heat between the bleed air and the outside air; a supply destination that is arranged to receive the bleed air passed through the heat exchanger; and a control section that is arranged to adjust a flow rate (q) of the bleed air supplied to the supply destination, wherein the control section includes a bleed air flow rate adjusting section that is arranged to adjust the flow rate (q) of the bleed air supplied to the supply destination, wherein the bleed air flow rate adjusting section uses a first relationship and a second relationship, the first relationship being a relationship between an altitude and a pressure upper limit that is an upper limit of pressure of the bleed air, the second relationship being a relationship between outside air temperature at which temperature of the bleed air reaches an allowable temperature of a member through which the bleed air flows and a pressure upper limit that is an upper limit of pressure of the bleed air, the second relationship being provided based on the altitude, when outside air temperature is lower than outside air temperature at an intersection of the first relationship and the second relationship, the bleed air flow rate adjusting section adjusts the flow rate (q) of the bleed air while suppressing the pressure (p) of the bleed air to the pressure upper limit or lower of the first relationship, and when the outside air temperature is higher than the outside air temperature at the intersection, the bleed air flow rate adjusting section adjusts the flow rate (q) of the bleed air while suppressing the pressure (p) of the bleed air to the pressure upper limit or lower of the second relationship. a heat exchanger that is arranged to exchange heat between the bleed air and the outside air; a supply destination that is arranged to receive the bleed air passed through the heat exchanger; and a control section that is arranged to adjust a flow rate (q) of the bleed air supplied to the supply destination, wherein the control section includes a bleed air flow rate adjusting section that is arranged to adjust the flow rate (q) of the bleed air supplied to the supply destination, wherein the bleed air flow rate adjusting section uses a first relationship and a second relationship, the first relationship being a relationship between an altitude and a pressure upper limit that is an upper limit of pressure of the bleed air, the second relationship being a relationship between outside air temperature at which temperature of the bleed air reaches an allowable temperature of a member through which the bleed air flows and a pressure upper limit that is an upper limit of pressure of the bleed air, the second relationship being provided based on the altitude, when outside air temperature is lower than outside air temperature at an intersection of the first relationship and the second relationship, the bleed air flow rate adjusting section adjusts the flow rate (q) of the bleed air while suppressing the pressure (p) of the bleed air to the pressure upper limit or lower of the first relationship, and when the outside air temperature is higher than the outside air temperature at the intersection, the bleed air flow rate adjusting section adjusts the flow rate (q) of the bleed air while suppressing the pressure (p) of the bleed air to the pressure upper limit or lower of the second relationship.