A block (A) for environmental maintenance available for both horizontal stacking and gradient stacking reasonably despite its being a unitary block. According to the invention, such block comprises a front wall (2) a rear bearing plate (4) inclined rearward, a coupling wall (1L, 1R) for coupling the front wall to the rear bearing plate, the front wall (2) forms a space zone (3) for planting and so on which is closed frontward independently or in cooperation with the front walls of blocks adjacent crosswise thereto, a projection (5R, L) is provided on a lower or upper surface of the coupling wall (1R, 1L), and on an upper or lower surface of the coupling wall (1L, 1R) corresponding thereto, there provided are a first recession (8, 11) engaging with the above-mentioned projection when upper-stage blocks are stacked up slidingly in a depth direction to lower-stage blocks and a second recession engaging with the projection when the upper- and lower- stage blocks are stacked up with the front walls kept facing alike.
