A heat collector tube according to the present invention is suitable for use in a direct steam generation-type solar energy system and heats a fluid which passed there through by the sunrays reflected thereon by means of at least one reflector. The heat collector tube (T) comprises at least one inner tube (1) of high heat conductivity, through which the fluid by which steam is generated is passed, and at least one spacer tube (2) which surrounds the inner tube (1) leaving a gap there between, on which sunrays fall, through which the gap made with the inner tube (1) at least one other fluid is passed, and which heats the fluid passed between the heat collector tube and the inner tube (1) by means of the sunrays falling thereon.