PURPOSE: To reduce the cost of a large retaining wall structure and to cope with diversification at a using site, in improvement of a large retaining wall having a wall height of approximately 5m or more.

CONSTITUTION: A large precast retaining wall block comprising a front vertical wall 15 having a retaining wall height exceeding approximately 50% of a whole, and a solid counterfort 4 is installed at a site as a lower structure 2. An upper structure 1 is built in a way that middle and small precast blocks 8 and 7 are stacked and a plastic net or an iron net 9 on which corrosion preventing treatment is applied are interlocked, where occasion demands.