To manufacture a thermoacoustic energy converting element part, a plurality of first plates and a plurality of second plates are formed. The first plate is provided with a plurality of linear penetration slits which are in parallel with each other and separated along a direction perpendicular to an extending direction of the slit. The slit penetrates the first plate in a thickness direction. The second plate is not provided with any penetration slit. A plate assembly is formed by layering some of the plurality of first plates between adjacent two of the plurality of second plates of which main surfaces face each other. The plate assembly is provided with a plurality of communicating passages formed with the penetration slits adjoining each other in a layering direction. Portions of the assembly at both ends in the extending direction of the penetration slits are cut off to open the communicating passages on both sides of the assembly.