PURPOSE: To provide a construction structure for a retaining wall which creates favorable environment for the growth of plants by giving allowance in the forward and backward directions by piling up retaining wall blocks stepwise and providing a space for plants on steps.

CONSTITUTION: A unit block consisting of a front wall 1 which expands in the right and left directions and a pair of side walls 2 which are connected behind the front wall 1 and expand in the forward and backward directions is used. Unit blocks which differ in depth are arranged by one step or a plurality of steps, respectively, and a unit block having large depth is arranged below a unit block having small depth to pile up unit blocks by several steps. Rear ends of the unit block at each step are aligned at the same vertical position and a PC steel bar 4 is stretched up and down to connect them integrally. Soil 6 for vegetation is filled in a clearance surrounded by the front wall 1 and the side walls 2 of the lower unit block which protrudes more forward and downward than the upper unit block to form a space 7 for vegetation.