An apparatus for estimating bio-information, the apparatus comprising: a pulse wave sensor configured to measure a current pulse wave signal from a user, the current pulse wave signal comprising at least a propagation wave (P1) and two reflection waves (P2, P3); and a processor configured to: determine a reference time interval between a plurality of reference element waveforms of a reference pulse wave signal that is measured in a reference posture, extract components from the at least one propagation wave and the at least two reflection waves of the current pulse wave signal, measure a current time interval between the components of the current pulse wave signal, determine whether a current measurement posture of the user corresponds to a reference posture based on a first comparison based on a first difference between the reference time interval and the current time interval and on a second comparison based on a second difference between a current heart rate measured in the current measurement posture and a reference heart rate measured in the reference posture, and estimate the bio-information based on a determination of whether the current measurement posture corresponds to the reference posture. a pulse wave sensor configured to measure a current pulse wave signal from a user, the current pulse wave signal comprising at least a propagation wave (P1) and two reflection waves (P2, P3); and a processor configured to: determine a reference time interval between a plurality of reference element waveforms of a reference pulse wave signal that is measured in a reference posture, extract components from the at least one propagation wave and the at least two reflection waves of the current pulse wave signal, measure a current time interval between the components of the current pulse wave signal, determine whether a current measurement posture of the user corresponds to a reference posture based on a first comparison based on a first difference between the reference time interval and the current time interval and on a second comparison based on a second difference between a current heart rate measured in the current measurement posture and a reference heart rate measured in the reference posture, and estimate the bio-information based on a determination of whether the current measurement posture corresponds to the reference posture. determine a reference time interval between a plurality of reference element waveforms of a reference pulse wave signal that is measured in a reference posture, extract components from the at least one propagation wave and the at least two reflection waves of the current pulse wave signal, measure a current time interval between the components of the current pulse wave signal, determine whether a current measurement posture of the user corresponds to a reference posture based on a first comparison based on a first difference between the reference time interval and the current time interval and on a second comparison based on a second difference between a current heart rate measured in the current measurement posture and a reference heart rate measured in the reference posture, and estimate the bio-information based on a determination of whether the current measurement posture corresponds to the reference posture. <EOS>