A biometric authentication device comprising: a storage unit configured to store for each of a plurality of users a respective reliability value and a respective item of enrollment feature data of a palm region of an imaged palm of the user in association with each of a plurality of subregions into which the palm region is divided, wherein each reliability value is indicative of an authentication reliability of the corresponding subregion; a biometric sensor configured to obtain a comparison-use biometric image of the palm of a user, a surface reflection component appearing in the comparison-use biometric image as a noise; an imaging unit configured to: receive a biometric image from the biometric sensor; extract comparison-use feature data for authentication from the comparison-use biometric image; and divide the comparison-use feature data into said plurality of subregions; and a surface reflection degree obtaining unit configured to obtain a surface reflection degree that is indicative of an existence ratio of surface reflection in the comparison-use biometric image for each of the subregions by detecting at least one of a luminance value and a high-frequency component in each subregion, an authentication process unit configured to: calculate a similarity between the comparison-use feature data and each of the stored enrollment feature data for each of the subregions; correct the similarities calculated for each subregion by using the reliability value associated with the subregion and the surface reflection degree obtained for the subregion such that the corrected similarity of each subregion increases with increasing reliability value and with decreasing surface reflection degree of the subregion; calculate a statistic amount of the corrected similarities for all enrolled users; compare the statistic amount for each subregion with a threshold; in the case where the statistic amount is larger than the threshold, determine that the user is an enrolled user; and in the case where the statistic amount is not larger than the threshold, determine that the user is not an enrolled user, the biometric authentication device further comprising a reliability process unit configured to update the reliability values based on the determination made by the authentication process unit. a storage unit configured to store for each of a plurality of users a respective reliability value and a respective item of enrollment feature data of a palm region of an imaged palm of the user in association with each of a plurality of subregions into which the palm region is divided, wherein each reliability value is indicative of an authentication reliability of the corresponding subregion; a biometric sensor configured to obtain a comparison-use biometric image of the palm of a user, a surface reflection component appearing in the comparison-use biometric image as a noise; an imaging unit configured to: receive a biometric image from the biometric sensor; extract comparison-use feature data for authentication from the comparison-use biometric image; and divide the comparison-use feature data into said plurality of subregions; and receive a biometric image from the biometric sensor; extract comparison-use feature data for authentication from the comparison-use biometric image; and divide the comparison-use feature data into said plurality of subregions; and a surface reflection degree obtaining unit configured to obtain a surface reflection degree that is indicative of an existence ratio of surface reflection in the comparison-use biometric image for each of the subregions by detecting at least one of a luminance value and a high-frequency component in each subregion, calculate a similarity between the comparison-use feature data and each of the stored enrollment feature data for each of the subregions; correct the similarities calculated for each subregion by using the reliability value associated with the subregion and the surface reflection degree obtained for the subregion such that the corrected similarity of each subregion increases with increasing reliability value and with decreasing surface reflection degree of the subregion; calculate a statistic amount of the corrected similarities for all enrolled users; compare the statistic amount for each subregion with a threshold; in the case where the statistic amount is larger than the threshold, determine that the user is an enrolled user; and in the case where the statistic amount is not larger than the threshold, determine that the user is not an enrolled user,