A data collation apparatus, comprising: a collation unit configured to calculate a similarity to indicate a degree of correspondence between input biometric data of an authentication subject which is measured by a measurement apparatus having at least one measurement parameter, and registered data which is stored in a storage apparatus in advance, for each of a plurality of registered data items respectively, the at least one measurement parameter being at least one of illumination intensity, direction, wavelength, exposure time, and focus position used for measurement; and a calculation unit configured to adjust the at least one measurement parameter, when a difference between the similarity of first registered data of which similarity with the input biometric data is highest and the similarity of second registered data of which similarity with the input biometric data is second highest, among the plurality of registered data items, is smaller than a first predetermined value, or when a degree of separation to indicate a distance between the similarity of the first registered data and a similarity distribution of a group of registered data items of which similarities with the input biometric data are second highest or lower than the similarity of the first registered data is smaller than a second predetermined value, based on at least the input biometric data and the first registered data, and to instruct the measurement apparatus to remeasure the authentication subject by using the adjusted at least one measurement parameter and to recalculate the similarity between the remeasured input biometric data and the registered data. a collation unit configured to calculate a similarity to indicate a degree of correspondence between input biometric data of an authentication subject which is measured by a measurement apparatus having at least one measurement parameter, and registered data which is stored in a storage apparatus in advance, input biometric data of an authentication subject which is measured by a measurement apparatus having at least one measurement parameter, and registered data which is stored in a storage apparatus in advance, for each of a plurality of registered data items respectively, the at least one measurement parameter being at least one of illumination intensity, direction, wavelength, exposure time, and focus position used for measurement; and a calculation unit configured to adjust the at least one measurement parameter, when a difference between the similarity of first registered data of which similarity with the input biometric data is highest and the similarity of second registered data of which similarity with the input biometric data is second highest, among the plurality of registered data items, is smaller than a first predetermined value, or when a degree of separation to indicate a distance between the similarity of the first registered data and a similarity distribution of a group of registered data items of which similarities with the input biometric data are second highest or lower than the similarity of the first registered data is smaller than a second predetermined value, based on at least the input biometric data and the first registered data, and to instruct the measurement apparatus to remeasure the authentication subject by using the adjusted at least one measurement parameter and to recalculate the similarity between the remeasured input biometric data and the registered data.