A hydroelectric power generator for a pipeline, comprising: a rectangular inlet pipe having an inlet port connected to an inlet pipe, and connected to an inlet through the inlet port; a pair of guide units (30, 30a) forming an upper drainage in which blades are deployed at an upper portion behind the inlet connected to the rectangular inlet pipe, a blade guide formed under the upper drainage so that the blades are reclined therein, and an outlet for discharging water flowing through the upper drainage; a turbine fitted on a turbine shaft disposed through the guide units (30, 30a), having reinforcing grooves fitted on two sides to reinforcing portions of the blades in blade seats formed with regular intervals on an outer side thereof, having fixed shafts disposed through the blade seats, having a narrow gap from a blade guide to recline the blades and a wide gap from the upper drainage to deploy the blades, combined with turbine covers on both sides by turbine screws to be rotatable inside the guide units (30, 30a) such that the turbine shaft rotates on bearings through the guide units (30, 30a); the blades disposed in the blade seats, coupled to the turbine covers through the fixed shaft, and rotating the turbine when deployed by water; and a rectangular outlet pipe connected to the outlet and having an outlet port connected to an outlet pipe, wherein a packing is disposed between the turbine covers coupled to both sides of the turbine and the blades are disposed in the blade seats formed with regular intervals, and the blades are fitted on the fixed shafts, are rotatably held at both sides by movable bushings, have an outer end protruding from the blade seats, and have the reinforcing portion fitted to two sides of the reinforcing grooves, wherein the inlet is upwardly curved from a horizontal state, is connected to the upper drainage on an upper side, and is connected to the blade guide on a lower side, the upper drainage and the blade guide converging to form the outlet on an opposite side of the inlet wherein each blade extends radially outwards when deployed in the upper drainage from a reinforcing portion and is rounded at the reinforcing portion, to fit to a blade seat,; a tip portion of the blade is partially protruded out of the blade seat in a folded state so as to be turned and deployed by water or to be folded by the blade guide, wherein the upper drainage is formed to have a predetermined gap from the ends of the blades to generate velocity heads when the blades are deployed and rotated, so that the same pressure is applied to the blades by water inside the upper drainage and torque corresponding to the number of the blades is applied to the turbine. a rectangular inlet pipe having an inlet port connected to an inlet pipe, and connected to an inlet through the inlet port; a pair of guide units (30, 30a) forming an upper drainage in which blades are deployed at an upper portion behind the inlet connected to the rectangular inlet pipe, a blade guide formed under the upper drainage so that the blades are reclined therein, and an outlet for discharging water flowing through the upper drainage; a turbine fitted on a turbine shaft disposed through the guide units (30, 30a), having reinforcing grooves fitted on two sides to reinforcing portions of the blades in blade seats formed with regular intervals on an outer side thereof, having fixed shafts disposed through the blade seats, having a narrow gap from a blade guide to recline the blades and a wide gap from the upper drainage to deploy the blades, combined with turbine covers on both sides by turbine screws to be rotatable inside the guide units (30, 30a) such that the turbine shaft rotates on bearings through the guide units (30, 30a); the blades disposed in the blade seats, coupled to the turbine covers through the fixed shaft, and rotating the turbine when deployed by water; and a rectangular outlet pipe connected to the outlet and having an outlet port connected to an outlet pipe, wherein a packing is disposed between the turbine covers coupled to both sides of the turbine and the blades are disposed in the blade seats formed with regular intervals, and the blades are fitted on the fixed shafts, are rotatably held at both sides by movable bushings, have an outer end protruding from the blade seats, and have the reinforcing portion fitted to two sides of the reinforcing grooves, wherein the inlet is upwardly curved from a horizontal state, is connected to the upper drainage on an upper side, and is connected to the blade guide on a lower side, the upper drainage and the blade guide converging to form the outlet on an opposite side of the inlet wherein each blade extends radially outwards when deployed in the upper drainage from a reinforcing portion and is rounded at the reinforcing portion, to fit to a blade seat,; a tip portion of the blade is partially protruded out of the blade seat in a folded state so as to be turned and deployed by water or to be folded by the blade guide, wherein the upper drainage is formed to have a predetermined gap from the ends of the blades to generate velocity heads when the blades are deployed and rotated, so that the same pressure is applied to the blades by water inside the upper drainage and torque corresponding to the number of the blades is applied to the turbine.