To manufacture at a low cost a small-sized thermal flow velocity sensor of which nonuniformity in an output characteristic is small and of which the accuracy and reliability are high.

A recessed part 52 is formed in one surface of a base 50, while a sacrifice layer 60 and a sensing layer 51 including a heat insulation film 54 provided with a heating resistor 57 and temperature measuring resistors 58A and 58B are formed on the other surface. As the result, a block 63 for lamination is formed. Next, the blocks 63 for lamination in a plurality are joined integrally so that the surface of one block 63 for lamination wherein the recessed part is formed and the surface of the sensing layer 51 of another block 63 for lamination are put on each other. When the sacrifice layers 60 are removed from the blocks 63 joined integrally, subsequently, the bases 50 and the sensing layers 51 are separated and a thermal flow velocity sensor is formed.