To provide an underground structure construction method according to which no unagitated region or no multiply agitated region under the ground exists, and labor and costs necessary for construction are reduced.

The underground structure construction method is comprised of a step of rotating excavating means (4, 80, 80A), and excavating a region immediately below the excavating means down to a predetermined depth; a step of ejecting fluid from fluid ejecting means (7, 71a, 71A, 71b) provided for the excavating means, and excavating and agitating earth in the region to be agitated; and a step of lifting up the excavating means which has reached the predetermined depth.