A small-sized hydraulic electrogenerating device comprises a base plate, a bracket device, a first idler wheel device, a support device, a frame body, a second idler wheel device and a buffer device, wherein a material receiving box is arranged on the base plate; the bracket device comprises a first support rod, a second support rod, a first sway rod, a second sway rod, a first vertical rod, a skew plate, a second vertical rod, a first cross bar and a first positioning block; the first idler wheel device comprises a first idler wheel and a first poke rod; the support device comprises a support plate, a first bracket and a third sway rod; a water collecting block, a filter screen, a first fixed block, a second fixed block, a second through hole and a water inlet pipe are arranged on the frame body; the second idler wheel device comprises a second idler wheel, a second poke rod, a curved pipe, a water inlet hopper, a first fixed rod, a second bracket and a second cross bar; the buffer device comprises a water outlet hopper, a third cross bar, a third vertical rod, a water outlet pipe, a second positioning block, a first spring, a top backup plate and a second spring. The small-sized hydraulic electrogenerating device can make full use of hydroenergy to reduce utilization of non-renewable energy resources.