A crash box capable of easily deforming into a bellows shape and absorbing impact energy more reliably, and its manufacturing method are provided. The present disclosure is applied to a crash box which is partly deformed in an axial direction to absorb impact energy when the crash box receives an impact in the axial direction. A first layer made of metal and a second layer made of metal containing a larger volume of bubbles than that of the first layer are alternately formed in the axial direction in the crash box according to the present disclosure.