A biological component estimation apparatus according to an aspect of the present invention includes: a light detector array including a plurality of light detectors; a plurality of light sources disposed on both ends of the light detector array; and a processor configured to calculate a blood vessel alignment index, which indicates a degree of alignment of the biological component estimation apparatus with respect to blood vessels, by using an intensity of a first light that is measured by the plurality of light detectors after the first light is emitted to a user's skin from a first light source disposed on one end of the light detector array among the plurality of light sources, and an intensity of a second light that is measured by the plurality of light detectors after the second light is emitted to the user's skin from a second light source disposed on the other end of the light detector array among the plurality of light sources.