There is provided a pulse wave detector in which the feeling and easiness of attachment to the wrist can be improved, and which can accurately detect a pulse wave, a biometric information measurement device including the detector, and an attachment auxiliary member which is to be used in a pulse wave detector. A biometric information measurement device 100 which is used while being attached to the wrist of a measurement subject includes: a housing 20 including a pulse wave detecting section 22； a strip-like band 40 for securing the housing 20 to the wrist W； and an attachment auxiliary member 30 which is configured to be attachable to and detachable from the band 40. In a secured state where the housing 20 is secured to the wrist W with the band 40 to which the attachment auxiliary member 30 is attached, the attachment auxiliary member 30 is contacted with the vicinity of the ulna S in the wrist W.
