To provide a construction method of a thermal insulation foundation having termite preventive performance, easy in construction, for surely preventing a wood part such as a sill of a wooden building from insect damage by a termite.

A form 10 is formed by erecting a pair of plate-like thermal insulation materials 11 and 21 at a predetermined distance on leveling concrete 5. A termite preventive mesh material 30 is arranged so that its lower end part 31 reaches a concrete filling space 19 by passing through between the outside thermal insulation material 11 of the form 10 and the leveling concrete 5, and its upper part 32 is hooked on an upper end surface part 14 of the outside thermal insulation material 11, and an end part 33 of the upper part 32 reaches the concrete filling space 19. An inside end part 52 is locked by a metallic cover 51 reaching the concrete filling space 19 so that the upper part 32 of the mesh material 30 is pressed to the upper end surface part 14 of the outside thermal insulation material 11.