PURPOSE: To decrease the cost and to enhance efficiency of recovery of mineral by constituting the machine of an inlet box and an outlet box provided on one vertical cylindrical floatation cell and a cell, a revolving mechanism for generating mineral-rich froth, and a hexagonal overflow froth launder for collecting mineral-rich froth. CONSTITUTION: A froth floatation machine 50 is provided with at least one of the vertical cylindrical floating cells 52-59 having the upper end, and the inlet boxes 64, 66 provided with the cells 52-59, and the outlet boxes 68, 70 provided on the cells 52-59. The machine is constituted such that revolving mechanisms 60, 61, 62 are respectively arranged in the cells 52, 54, 56 in order to generate mineral-rich froth, and the entire periphery of the upper end of the cells 52-56 is extended around it in order to collect the mineral-rich froth, and hexagonal overflow froth launders 84, 88, 89 and 94 are attached to the upper end.