The present invention relates to an electric massage device capable of gradually increasing a massage force during an outward stroke, mainly comprising a massage module and a control module. In the outward stroke, the control module applies a driving current to the electromagnetic driving unit, and the driving current is gradually increased with an elapsed time or a stroke displacement of the output shaft. In a return stroke, the control module deenergizes the driving current or applies a weak reverse current less than one-fifth of the driving current. At the beginning of the outward stroke, the massage force is weak due to the smaller driving current and hence would not cause skin hurt. At the end of the outward stroke, the massage force is strong due to the greater driving current and hence produces a deep muscle massage effect.