A fan unit connectable to a first unit through a duct which distributes air delivered from the first unit to the fan unit, the fan unit comprising: a fan that supplies air to a target space; a casing that has an intake port and a blow-out port and houses the fan; a first acquisition unit that acquires a rotation speed (Nx) of a fan motor that drives the fan; a second acquisition unit that acquires information about at least one from among a volume of air (Qx), a wind speed (Vx), and front-rear differential pressure (ΔPx) that is a difference in air pressure between the intake port and the blow-out port of the casing, of the fan; a third acquisition unit that acquires an air volume target value (Qy) or a wind speed target value (Vy) for the fan; and a control unit that controls the rotation speed (Nx) of the fan motor to a rotation speed target value (Ny) corresponding to the air volume target value (Qy) or the wind speed target value (Vy) for the fan; the rotation speed (Nx) of the fan motor, the volume of air (Qx) or the wind speed (Vx) of the fan, and the front-rear differential pressure (ΔPx) are parameters having a relation in which, from two acquired values of them, the control unit is configured to derive the remaining one value, and the control unit is configured to use a first function and a second function that use, as variables, the rotation speed (Nx) of the fan motor, the volume of air (Qx) or the wind speed (Vx) of the fan, the front-rear differential pressure (ΔPx), and the air volume target value (Qy) or the wind speed target value (Vy) for the fan,wherein the control unit is configured to calculate the rotation speed target value (Ny) for the fan motor by the first function, or to calculate a required rotation speed change amount (ΔN) for the fan motor by the second function and to calculate the rotation speed target value (Ny) on the basis of the calculated required rotation speed change amount (ΔN). a fan that supplies air to a target space; a casing that has an intake port and a blow-out port and houses the fan; a first acquisition unit that acquires a rotation speed (Nx) of a fan motor that drives the fan; a second acquisition unit that acquires information about at least one from among a volume of air (Qx), a wind speed (Vx), and front-rear differential pressure (ΔPx) that is a difference in air pressure between the intake port and the blow-out port of the casing, of the fan; a third acquisition unit that acquires an air volume target value (Qy) or a wind speed target value (Vy) for the fan; and a control unit that controls the rotation speed (Nx) of the fan motor to a rotation speed target value (Ny) corresponding to the air volume target value (Qy) or the wind speed target value (Vy) for the fan; the rotation speed (Nx) of the fan motor, the volume of air (Qx) or the wind speed (Vx) of the fan, and the front-rear differential pressure (ΔPx) are parameters having a relation in which, from two acquired values of them, the control unit is configured to derive the remaining one value, and the control unit is configured to use a first function and a second function that use, as variables, the rotation speed (Nx) of the fan motor, the volume of air (Qx) or the wind speed (Vx) of the fan, the front-rear differential pressure (ΔPx), and the air volume target value (Qy) or the wind speed target value (Vy) for the fan,wherein the control unit is configured to calculate the rotation speed target value (Ny) for the fan motor by the first function, or to calculate a required rotation speed change amount (ΔN) for the fan motor by the second function and to calculate the rotation speed target value (Ny) on the basis of the calculated required rotation speed change amount (ΔN).