PROBLEM TO BE SOLVED: To provide floor construction device for the construction of floor surface on grass ground upon holding an event, such as concert, in which grass ground where grass has grown, such as stadium, is utilized.SOLUTION: The device is consisting of protection mat (1) laid on grass ground and flooring material (2) laid thereon. The protection mat (1) comprises first net component (10A) and second net component (10B) in which a large number of line material (10a,10b) are aligned in parallel respectively, in which upward hill part (12a,13a) and downward hill part (12b,13b) are mutually formed in axis direction. The first net component and second net component are mutually laminated from upward and downward in a manner where the line material (10a,10b) crosses and fixes cross parts so as to construct a net shape sheet plate (11) having a predetermined net shape. A grounding part (15) is formed with the downward hill part (13b) of the line material (10b) in lower net component and a supporting part (16) supporting flooring material (2) is formed with the upward hill part (12a) of the line material (10a) in upper component.SELECTED DRAWING: Figure 8
