Biological information acquisition device and biological information acquisition method

A biometric information acquisition method performed by a biometric information acquisition device capable of acquiring a captured image obtained by capturing an image of a fingertip of a subject, the biological information acquisition method comprising:

• capturing an image of a finger of the subject in a non-contact state under a first focus control by a camera;
• acquiring a first captured image captured under the first focus control;
• measuring a size of the fingertip of the subject with respect to an entire area of the first captured image;
• determining a focus step size of the camera for capturing an image under a second focus control different from the first focus control based on the size of the fingertip;
• capturing an image within a focus section, within which an image is captured, at the focus step size by the second focus control by the camera;
• and
• acquiring any one second captured image among M (M is an integer of 2 or more) second captured images captured under the second focus control.