An apparatus for measuring a bio-signal includes: a light source configured to emit light; an ultrasonic transducer configured to obtain a photoacoustic signal generated from an object; a photoacoustic coupler disposed in contact with the ultrasonic transducer and configured to direct the light transmitted from the light source to a scanner and to direct the photoacoustic signal generated from the object to the ultrasonic transducer; the scanner configured to reflect the light incident from the photoacoustic coupler to the object, and reflect the photoacoustic signal generated from the object to the photoacoustic coupler; a scanner controller configured to adjust a light incident position on the object by controlling the angle of the scanner; a light detector configured to obtain a light signal by detecting the light scattered or reflected from the object; and a processor configured to obtain bio-information based on the light signal and the photoacoustic signal.