The present invention relates to an automatic tension measurer, comprising: a band lengthily formed in a longitudinal direction; a main body formed to allow the band to be guided thereinto such that one-side end portion of the band is fixed and the other-side end portion thereof is drawn to the outside; a marking part implemented in the main body, and formed so as to enable marking in the band at a specific position in response to the tension applied to the band; and a stopper formed in the main body, and stopping the band at a specific position.