The invention discloses an energy-absorbing device and a safety seat using the energy-absorbing device. The energy-absorbing device is assembled between the back frame edge of a floating frame and the back frame edge of a positioning frame; the energy-absorbing device is provided with an energy-absorbing piece which is arranged vertically; the energy-absorbing piece is provided with an expansion seam extending along a vertical direction; the width of the expansion seam is reduced gradually along the vertical direction; a force delivery column is inserted into the larger end of the expansion seam; a connecting piece is fixedly connected to the force delivery column; opposite ends of the connecting piece and the energy absorbing piece are provided with a connecting structure and a hinging structure respectively. During collision of the front part of a vehicle, the upper half bodies of passengers and a driver drive chair backs to tilt forwards through safety belts, the back frame edge of the floating frame is used for tensioning the back frame edge of the positioning fame through the energy absorbing device, and the connecting piece in the energy absorbing device is used for pulling the force delivery column inside from the larger end to the smaller end of the expansion seam on the energy absorbing piece in a tensioning process in order to deform the energy absorbing piece while opposite side walls of the expansion seam are expanded through the force delivery column, so that the forward tilting impact force on the seat is relieved.