This driver condition assessment device assesses the condition of the driver of a host vehicle by assessing whether a prescribed driving operation has been performed. The driver condition assessment device (1) is equipped with: a running condition detection means that detects the running condition of the host vehicle; a size detection means that detects the size of a preceding vehicle located in front of the host vehicle; an awareness decrease determination means that determines that the awareness of the driver of the host vehicle has decreased when the running condition detected by the running condition detection means exceeds a prescribed threshold value; and a threshold value setting means that sets the threshold value in response to the size of the preceding vehicle detected by the size detection means.