To provide a structure installation mount, capable of firmly supporting even many solar cell modules, with a few component parts, allowing easy construction work.

A structure installation mount construction method comprises following processes: a pipe 25 is inserted between each lateral plate 15a of a first crosspiece member 151; a bolt hole 15f of each lateral plate 15a of the first crosspiece member 151 and a bolt hole 15f of each lateral plate 15a of a second crosspiece member 152 are positioned; a bolt 26 is inserted into the pipe 25, the bolt hole 15f of each lateral plate 15a of the first crosspiece member 151, the bolt hole 15f of each lateral plate 15a of the second crosspiece member 152 and a washer; the end of the bolt 26 is screwed into a nut 27 and tightened; and each lateral plate 15a of the second crosspiece member 152 is connected to each lateral plate 15a of the first crosspiece member 151.