A small hydropower of a novel concept, comprising: two side supports; a main rotation axis provided on the upper end between the two side supports; a rotation body for rotating around the main rotation axis; fillable-then-emptiable water containers which are provided around the circumference of the rotation body, remain horizontally level, add weight by being filled with a certain amount of water when positioned at the top center of the rotation body during rotation, and remove the weight by spilling when positioned at the bottom center; a selective water supply device which can provide, to a fillable-then-emptiable water container that is positioned at the top center of the rotation body, water, and which temporarily stops discharging water until the next fillable-then-emptiable water container is positioned, if one fillable-then-emptiable water container is completely filled.