PURPOSE: A boundary block for a road way and a sidewalk is provided to improve construction efficiency by connecting continuously the boundary blocks with assembling grooves, assembling projections, and hanging sills and to increase the rigidity of the boundary block. CONSTITUTION: A vegetating space(2) for planting trees is formed in a boundary block(1) installed at the boundary of a road way and a sidewalk and a partition(3) for dividing the vegetating space is formed in the vegetating space. Assembling projections(4) and assembling grooves for connecting longitudinally and assembling the boundary blocks to each other are formed at both upper sides of the boundary block. Hanging grooves(6) for suspending and lifting the boundary block are formed under the assembling projections and grooves. A hanging sill(7) for suspending a pavement block and reinforcing the boundary block is disposed horizontally in the rear side of the boundary block. A wire net(8) for blocking up a lower part of the vegetating space is mounted at the lower side of the boundary block. A luminous paint layer(9) is coated over the front side of the boundary block.