The invention relates to a dysmenorrhea relieving system using a transcutaneous electrical nerve stimulator (TENS), and a method for relieving dysmenorrhea by using a low-frequency dysmenorrhea relieving system, the method comprising: an attachment step (s100) for attaching, to the body or clothing of a user, a body of the dysmenorrhea relieving system which comprises a low-frequency generation module for the TENS, a display unit, and a control unit for controlling the low-frequency generation module and the display unit; an attachment step (s200) for attaching, to the body of the user, an electrode pad connected to the low-frequency generation module; a step (s300) of selecting, through an input unit, one of a plurality of low-frequency generation modes programmed and prestored in a memory of the control unit of the body; a step (s400) of displaying information on the selected low-frequency generation mode on the display unit; and a step (s500) of generating, in the low-frequency generation module, a low frequency corresponding to the selected low-frequency generation mode among the low-frequency generation modes preprogrammed.