An apparatus for estimating bio-information, the apparatus comprising: a pulse wave sensor (110, 210, 220) including a plurality of channels (211, 212), each channel of the plurality of channels (211, 212) being configured to measure (911, 912) a first pulse wave signal of a first wavelength and a second pulse wave signal of a second wavelength that is different from the first wavelength, the pulse wave sensor (110, 210, 220) comprising at least one light source (211a, 211c, 212a, 212c, 221a, 221b) configured to emit light of the first wavelength and light of the second wavelength onto an object, and at least one light receiver (211b, 211d, 212b, 212d, 222a-d) configured to detect the light of the first wavelength and the light of the second wavelength, which is scattered or reflected from the object; and a processor (120, 300) configured to: for each channel of the plurality of channels (211, 212), generate a first oscillogram based on the first pulse wave signal, generate a second oscillogram based on the second pulse wave signal, and convert a phase delay between the first oscillogram and the second oscillogram into an area in a Lissajous waveform, determine a channel among the plurality of channels (211, 212) based on the area of each channel, and estimate bio-information based on the determined channel, wherein an oscillogram refers to a correlation between a change in contact pressure, applied by the object to the pulse wave sensor (110, 210, 220), and an amplitude of the pulse wave signal. a pulse wave sensor (110, 210, 220) including a plurality of channels (211, 212), each channel of the plurality of channels (211, 212) being configured to measure (911, 912) a first pulse wave signal of a first wavelength and a second pulse wave signal of a second wavelength that is different from the first wavelength, the pulse wave sensor (110, 210, 220) comprising at least one light source (211a, 211c, 212a, 212c, 221a, 221b) configured to emit light of the first wavelength and light of the second wavelength onto an object, and at least one light receiver (211b, 211d, 212b, 212d, 222a-d) configured to detect the light of the first wavelength and the light of the second wavelength, which is scattered or reflected from the object; and a processor (120, 300) configured to: for each channel of the plurality of channels (211, 212), generate a first oscillogram based on the first pulse wave signal, generate a second oscillogram based on the second pulse wave signal, and convert a phase delay between the first oscillogram and the second oscillogram into an area in a Lissajous waveform, determine a channel among the plurality of channels (211, 212) based on the area of each channel, and estimate bio-information based on the determined channel, for each channel of the plurality of channels (211, 212), generate a first oscillogram based on the first pulse wave signal, generate a second oscillogram based on the second pulse wave signal, and convert a phase delay between the first oscillogram and the second oscillogram into an area in a Lissajous waveform, determine a channel among the plurality of channels (211, 212) based on the area of each channel, and estimate bio-information based on the determined channel, wherein an oscillogram refers to a correlation between a change in contact pressure, applied by the object to the pulse wave sensor (110, 210, 220), and an amplitude of the pulse wave signal.