NOVELTY - The method involves determining whether operation sound generation of an environment-friendly vehicle is performed according to working condition of the vehicle. Operation sound is changed according to a sensing signal. A connected state of a sound output part (800) and an operating state of a sound source player (600) are confirmed. Output of a sound source amplification unit (700) is compared with a reference value by a control unit (400). Judgment is made to check whether electric connection condition of the sound output part is normal. Operation of the sound source player is controlled.    USE - Method for controlling an operation sound generating device (claimed) of an environment-friendly vehicle. Uses include but are not limited to a hybrid vehicle, an electric vehicle, a hydrogen fuel cell vehicle, petrol vehicle and diesel vehicle.    ADVANTAGE - The method enables sensing different operating states of the vehicle and reproducing different types of operation sounds according to sensed working condition of the vehicle so as to deliver operation sound about movement feeling of an operator and a pedestrian according to working condition of the vehicle, so that safe operation of the operator can be ensured, thus securing safety of the pedestrian. The method enables guiding different states of the vehicle such as battery charger connected state or charge power energy residual amount notice state of the vehicle through the operation sound so as to enable the operator to easily and clearly recognize state of the vehicle and vehicle drive operation, so that administration of the vehicle can be conveniently performed. The method enables determining whether driving sound or engine noise is occurred during normal operation at an initial state of the vehicle and judging whether distortion of acoustic output is occurred so as to safely prevent occurrence of accident production possibility among driving due to non-operation.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for an operation sound generating device of an environment-friendly vehicle.    DESCRIPTION OF DRAWING(S) - The drawing shows a block diagram of an operation sound generating device of an environment-friendly vehicle. '(Drawing includes non-English language text)'    Communication unit (300)    Control unit (400)    Sound source player (600)    Sound source amplification unit (700)    Sound output part (800)