PROBLEM TO BE SOLVED: To enable a ventilation window having a solid structure to be inexpensively formed in a plastic greenhouse having a pipe structure, suitable for agriculture and horticulture, and capable of being built at an inexpensive constructing cost. SOLUTION: This pipe-type plastic greenhouse is obtained by using a pipe structure characterized by two-piece structures of each arch pair divided at the ridge parts so that the pipe structures having arch shapes may be composed, and previously set different lengths of the legs of the divided arches so that the arch pairs 1a and 1b divided at the ridge parts may be connected at the ridge parts while shifting the positions in the upper and lower direction. The space H between the ridge parts at the upper row and the ridge parts at the lower row is formed into the ventilation window.
