An authentication method includes projecting a near infrared (NIR) ray using a light emitting diode (LED) of a terminal, receiving a light reflected by a vein of a user using an image sensor of the terminal, verifying whether an image generated using the received light exhibits a vein pattern, in response to the image generated using the received light being verified as exhibiting the vein pattern, generating a vein pattern of the vein based on an image generated using the received light, and in response to the generated vein pattern being determined to match a pre-stored vein pattern, authenticating the user as a registered user corresponding to the pre-stored vein pattern.