To keep the ground in a smooth or almost smooth state by strongly pressing keeping equipment with a large ground contact area against the ground so as to bring the keeping equipment into close contact with the ground, or by mounting a ground scraping implement so as to alternately repeat scraping operation and smoothing operation a plurality of times.

A top board 3 with the same number of oblique grooves 20, 20... with almost the same dimensions is stuck in the same position on artificial turf 10 with oblique grooves formed by cutting out a plurality of grooves 2, 2... in an oblique direction with respect to a rectangle, except sections near side surfaces on both the long sides of the almost rectangular artificial turf 1 and sections near side surfaces on both the short sides thereof. Additionally, a rectangular weight plate 4 with almost the same dimensions is arranged thereon.