The invention relates to a breast-firming arm training device which comprises an elastic device, a handheld device and a fixed connection device. The elastic device is slidably connected with the handheld device, and the fixed connection device is fixedly connected with the elastic device. By the changing of the position of the handheld device, resistance generated by the elastic device is overcome, and the objective of keep-fit exercise and strength enhancing is achieved. Besides, the resistance is linear force opposite in directions, so that no sense of pressure is caused to the human body, and the effect of healthy exercise is achieved. By the changing of the direction and distance between the breast-firming arm training device and the ground, multi-azimuth and multi-pose exercise is performed, and muscle groups capable of being enhanced by the breast-firming arm training device are more comprehensive.