Abstract: The present invention enables frequency response in a wide band without lowering the Q value. This vibrational energy harvester device is provided with: a movable part capable of vibration in a vibration direction as a result of mechanical vibrational energy applied from the exterior, said movable part being provided with a first surface along the vibration direction; and a fixed part provided with a second surface facing the first surface of the movable part with an interval therebetween, said fixed part being configured so as to be positionally fixed even against vibrational energy. A plurality of projections protruding in a direction orthogonal to the vibration direction are formed so as to be arranged like comb teeth in the vibration direction on each of the first surface of the movable part and the second surface of the fixed part. An electret film is formed on at least the first surface of the fixed part or on at least the second surface of the movable part.