PURPOSE: To efficiently and exactly perform the green-planting work of slope by a method in which high-pressure water is jetted onto a sloped ground to excavate holes of given width and depth, and a subgrade consisting of soil, seeds and fertilizer is formed for green-planting work.

CONSTITUTION: High-pressure water is jetted onto sloped ground 1 from a nozzle 2 connected to a high-speed jetter to form a trench 3 of a given depth (h), and trenches 3' are likewise formed at intervals. The ground 1 between the trenches 3 and 3' is excavated to form a hole 4, and a mixture of soil, seeds and fertilizer is packed into the hole 4. The excavation work of hard ground can be made simply and efficiently, and formation of the trenches and subgrade for green- planting work in wide area can thus be performed economically.