A blood vessel image capturing apparatus, comprising: a position area on which a finger can be placed; a light source configured to irradiate the finger presented on the position area; an imaging unit configured to form an image of light emitted from the light source and transmitted through the finger; a pressure detecting unit with at least four pressure sensors (23-a, 23-b, 23-c, 23-d) provided at four locations, configured to detect pressure of the finger placed on the position area; and an image processing unit configured to: process an image formed by the imaging unit, extract a finger contour, and obtain a position of a pressed region where the pressure of the finger is at or more than a predetermined pressure value, wherein the image processing unit is further configured to: determine a pressure vector which is defined as having a direction towards the center of the pressed region that is determined according to a ratio of the pressure values of the four pressure sensors (23-a, 23-b, 23-c, 23-d), calculate a similarity between the pressure vector and a registered pressure vector determined from each of previously registered plural images, and select, according to the calculated similarity, a registered image of the registered plural images to be collated with the image. a position area on which a finger can be placed; a light source configured to irradiate the finger presented on the position area; an imaging unit configured to form an image of light emitted from the light source and transmitted through the finger; a pressure detecting unit with at least four pressure sensors (23-a, 23-b, 23-c, 23-d) provided at four locations, configured to detect pressure of the finger placed on the position area; and an image processing unit configured to: process an image formed by the imaging unit, extract a finger contour, and obtain a position of a pressed region where the pressure of the finger is at or more than a predetermined pressure value, wherein the image processing unit is further configured to: determine a pressure vector which is defined as having a direction towards the center of the pressed region that is determined according to a ratio of the pressure values of the four pressure sensors (23-a, 23-b, 23-c, 23-d), calculate a similarity between the pressure vector and a registered pressure vector determined from each of previously registered plural images, and select, according to the calculated similarity, a registered image of the registered plural images to be collated with the image. process an image formed by the imaging unit, extract a finger contour, and obtain a position of a pressed region where the pressure of the finger is at or more than a predetermined pressure value, wherein the image processing unit is further configured to: determine a pressure vector which is defined as having a direction towards the center of the pressed region that is determined according to a ratio of the pressure values of the four pressure sensors (23-a, 23-b, 23-c, 23-d), calculate a similarity between the pressure vector and a registered pressure vector determined from each of previously registered plural images, and select, according to the calculated similarity, a registered image of the registered plural images to be collated with the image. determine a pressure vector which is defined as having a direction towards the center of the pressed region that is determined according to a ratio of the pressure values of the four pressure sensors (23-a, 23-b, 23-c, 23-d), calculate a similarity between the pressure vector and a registered pressure vector determined from each of previously registered plural images, and select, according to the calculated similarity, a registered image of the registered plural images to be collated with the image.