A fan structure is provided, which includes: a fan case having an inlet and an outlet; a bladed wheel provided inside the fan case; a motor for rotating the bladed wheel; a circuit substrate for controlling the motor; and a scroll housing formed between the fan case and the bladed wheel. Rotation of the bladed wheel causes a fluid to enter the scroll housing from the inlet and to exit from the outlet. The circuit substrate and the motor are arranged inside the fan case. The fan structure further includes a waterproof member for dividing the motor and the circuit substrate from the scroll housing, and a cylindrical seal for sealing a hole formed in the waterproof member through which an output shaft of the motor extends. The fan structure is compact and prevents adhesion of salt, water, or dust to the built-in circuit substrate.