An electrical power generation device for bicycles is disclosed. Said electrical power generation device comprises one or more magnetic elements (4) to be propellably attached to a bicycle and an energy conversion unit (1) to be fixedly attached to the bicycle, where the energy conversion unit (1) includes a piezoelectric transducer (2) operatively connected to a ferromagnetic piece (3), the one or more magnetic elements (4) being arranged to be moveable past the ferromagnetic piece (3) such that a magnetic force is exertable on the ferromagnetic piece (3), the ferromagnetic piece (3) being deflectable when the one or more magnetic elements (4) are located in close proximity of the ferromagnetic piece (3). The mechanical stress/strain imposed on the piezoelectric transducer (2) when it is bent due to the deflection of the ferromagnetic piece (3) generates a voltage (V) across the terminals of the piezoelectric transducer (2), which is subsequently converted into usable electrical power.