To provide a fluid filter device for an automatic speed change gear reducing the number of parts and exclusive manufacturing processes which is inexpensive and provided with sufficient strength.

In a fluid filter device 10 for an automatic speed change gear formed of an upper case 1 with a flow outlet, a lower case 2 with a flow inlet having a protruded section and a filter 5 interposed between the upper and lower cases 1 and 2, a caulking section for caulking and fixing the filter 5 is disposed on the flow inlet 4, and the protruded section and the caulking section are formed integrally with the lower case 2.