An operator state determining device , comprising: an image pick-up device to be disposed inside a cabin of a vehicle, and configured to image an operator from a side, the image pick-up device also being configured as a torso angle detector configured to detect an initial torso angle of the operator ; and a processor configured to measure a head-pitch angle change (Δθp), based on image data of the operator captured by the image pick-up device , wherein the head-pitch angle change (Δθp) is a difference between a head-pitch angle (θp11, θp21) of the operator before the operator becomes unconscious and a head-pitch angle (θp12, θp22) of the operator after the operator becomes unconscious; characterized by a memory configured to store a given angle (θ0) between 30° and 35° and a given head-pitch angle change (θ3), wherein the processor is further configured to determine whether the initial torso angle (θt) is equal to or greater than the given angle (θ0), and the head-pitch angle change (Δθp) is equal to or greater than the given head-pitch angle change (θ3), wherein the initial torso angle (θt) is an inclination angle of a seat back with respect to a vertical direction, wherein the processor is configured to measure a torso angle change (Δθt), wherein the torso angle change (Δθt) is a difference between the initial torso angle (θt), which is detected by the torso angle detector before the operator becomes unconscious, and a torso angle (θt) after the operator becomes unconscious, wherein the memory is configured to store a given second head-pitch angle change (θ1) and a given torso angle change (θ2), and wherein the processor is configured to determine whether the initial torso angle (θt) is less than the given angle (θ0), the head-pitch angle change (Δθp) is equal to or greater than the given second head-pitch angle change (θ1), and the torso angle change (Δθt) is equal to or greater than the given torso angle change (θ2). an image pick-up device to be disposed inside a cabin of a vehicle, and configured to image an operator from a side, the image pick-up device also being configured as a torso angle detector configured to detect an initial torso angle of the operator ; and a processor configured to measure a head-pitch angle change (Δθp), based on image data of the operator captured by the image pick-up device , wherein the head-pitch angle change (Δθp) is a difference between a head-pitch angle (θp11, θp21) of the operator before the operator becomes unconscious and a head-pitch angle (θp12, θp22) of the operator after the operator becomes unconscious; characterized by a memory configured to store a given angle (θ0) between 30° and 35° and a given head-pitch angle change (θ3), wherein the processor is further configured to determine whether the initial torso angle (θt) is equal to or greater than the given angle (θ0), and the head-pitch angle change (Δθp) is equal to or greater than the given head-pitch angle change (θ3), wherein the initial torso angle (θt) is an inclination angle of a seat back with respect to a vertical direction, wherein the processor is configured to measure a torso angle change (Δθt), wherein the torso angle change (Δθt) is a difference between the initial torso angle (θt), which is detected by the torso angle detector before the operator becomes unconscious, and a torso angle (θt) after the operator becomes unconscious, wherein the memory is configured to store a given second head-pitch angle change (θ1) and a given torso angle change (θ2), and wherein the processor is configured to determine whether the initial torso angle (θt) is less than the given angle (θ0), the head-pitch angle change (Δθp) is equal to or greater than the given second head-pitch angle change (θ1), and the torso angle change (Δθt) is equal to or greater than the given torso angle change (θ2). <EOS>