Abstract: A hydroelectric apparatus includes multiple propellers to be driven by a hydraulic current, a generating module and a transmission arranged between the propellors and the generating module. Thus, the rotation of the propellors is convertible into electricity. The transmission is used to change a rotational speed of the set of propellers. The propellors are able to float on water in a canal without affecting the performance of the canal. The number of the propellors is large to produce a large torque to increase the power of the hydroelectric apparatus so that the electricity can be supplied to the public. Moreover, the small size of the hydroelectric apparatus renders the hydroelectric apparatus inexpensive and environmentally friendly.