A driving assistance device comprising: a biometric information obtaining unit configured to obtain biometric information of a driver; a driver state estimating unit configured to estimate, on the basis of the biometric information obtained by the biometric information obtaining unit, a state of the driver at a time later than a timing of obtaining the biometric information by the biometric information obtaining unit; and a control unit configured to control driving assistance of a vehicle on the basis of a comparison of the state of the driver estimated by the driver state estimating unit with a condition for the state of the driver that is set in association with any one of a position and an environment in which the vehicle driven by the driver is predicted to travel, wherein the state of the driver is a concentration level of the driver; and wherein the driver state estimating unit, on the basis of the biometric information obtained by the biometric information obtaining unit, is configured to estimate a tendency of the concentration level of the driver to decrease over time wherein the control unit; is configured to call to the attention of the driver when the state of the driver estimated by the driver state estimating unit is below a first threshold and is configured to perform the driving assistance of intervening in a driving operation by the driver when the state of the driver estimated by the driver state estimating unit is below a second threshold that is lower than the first threshold, wherein the first threshold is set as a higher value than a lower limit of the concentration level that is required for the driver to drive on a road which is predicted to be traveled by the vehicle. a biometric information obtaining unit configured to obtain biometric information of a driver; a driver state estimating unit configured to estimate, on the basis of the biometric information obtained by the biometric information obtaining unit, a state of the driver at a time later than a timing of obtaining the biometric information by the biometric information obtaining unit; and a control unit configured to control driving assistance of a vehicle on the basis of a comparison of the state of the driver estimated by the driver state estimating unit with a condition for the state of the driver that is set in association with any one of a position and an environment in which the vehicle driven by the driver is predicted to travel, wherein the state of the driver is a concentration level of the driver; and wherein the driver state estimating unit, on the basis of the biometric information obtained by the biometric information obtaining unit, is configured to estimate a tendency of the concentration level of the driver to decrease over time wherein the control unit; is configured to call to the attention of the driver when the state of the driver estimated by the driver state estimating unit is below a first threshold and is configured to perform the driving assistance of intervening in a driving operation by the driver when the state of the driver estimated by the driver state estimating unit is below a second threshold that is lower than the first threshold, wherein the first threshold is set as a higher value than a lower limit of the concentration level that is required for the driver to drive on a road which is predicted to be traveled by the vehicle.