PROBLEM TO BE SOLVED: To estimate recognition degree of a driver from less parameters.SOLUTION: A driving assisting device 10 which is a recognition degree estimation device includes a recognition degree estimation part 1044 which estimates a recognition degree which represents degree of concentration of a driver 20 on driving based on only vertical movement of the line of sight of the driver 20 of a vehicle. The recognition degree estimation part 1044 detects a vertical position of the line of sight for each predetermined sampling cycle, and performs frequency analysis with a detection value of a position of the line of sight within a predetermined time period. If an integration value in a predetermined frequency band of the frequency analysis result exceeds a predetermined threshold value, it is estimated that a recognition degree of the driver has dropped.
