To provide a building method for a target mound which does not require many working machines and work preparatory materials such as heavy machines or carrying vehicles for soil and gravel, and can shorten the building period of time.

When the approximately circular target mound of which the diameter is 7 m to 25 m when the whole is viewed on a plane is built, the target mound is divided and formed into piece blocks which are plurality of squares in the longitudinal and lateral directions when viewed on the plane, and are made of an expanded polystyrene. Then, a sheet having a specified size is laid at a target installation spot, and the plurality of piece blocks are placed on the sheet, and thus, a base mound is formed. Then, a sheet is placed on the base mound, and at the same time, a cushioning material is placed. Then, an artificial turf is laid on the surface of the cushioning material for the constitution.