A thermal type air flow meter that is capable of suppressing deformation of a base member at the time of molding is disclosed, to thereby secure dimension accuracy and reduce an influence of a dimension change on measuring accuracy. The meter includes a housing member placed in an intake passage of an internal combustion engine, and a base member fixed to the housing member and includes a secondary air passage into which part of air passing through the intake passage flows. The base member is a plate-like resin molded component formed of a synthetic resin material and includes a reinforcing structure integrally formed between a board fixing part to which a circuit board is fixed; and a secondary passage constituting part formed at a leading end part of the board fixing part, the reinforcing structure enhancing strength of the base member.