PROBLEM TO BE SOLVED: To provide a hollow tube for a greenhouse which may be cheaply produced by utilizing a conventional hollow tube producing facility, have high fastening strength a variety of joints such as cross, and have easiness in machining to make curve.SOLUTION: A hollow tube for a greenhouse is consisting of a combination of: a hollow straight tube entirely having straight octagonal section in a longitudinal direction； and a hollow curve tube having straight octagonal section comprising a straight eave part at one end, an approximate straight roof part at the other end and a curve part curved in an arced-shape at middle section. The hollow curve tube comprises flat surfaces at a curve outer surface at the outermost position of the curve part and at a curve inner surface at the innermost position. In addition, at least parts of surfaces of the hollow curve tube and the hollow straight tube have increased friction coefficient by satin-finish processing for forming rough surfaces.
