A traveling control device for mounting on a vehicle and performing traveling control on the vehicle, the traveling control device comprising: an externality recognition information acquisition unit that receives externality recognition information from an externality sensor ascertaining target objects outside the self-vehicle including an obstacle and another vehicle on a route or receives information from a road side through out-of-vehicle communication to acquire the externality recognition information; a driving behavior decision unit that decides driving behavior content to be taken by the self-vehicle based on the externality recognition information received from the externality recognition information acquisition unit and self-vehicle information which is information including a position and a traveling speed of the self-vehicle; a driving behavior cause specifying unit that specifies a driving behavior cause as a reason why the driving behavior content received from the driving behavior decision unit is decided; a driving behavior information output unit that outputs the driving behavior content and the driving behavior cause specified in regard to the driving behavior content; a traveling control content decision unit that decides traveling control content of the vehicle based on a driving behavior decided by the driving behavior decision unit; a traveling control cause specifying unit that specifies a traveling control cause as a reason why the traveling control content is decided; a traveling control information output unit that outputs the traveling control content and the specified traveling control cause; a traveling control discomfort determination unit that determines whether the traveling control gives discomfort to an occupant of the vehicle in regard to a combination of the traveling control content and the traveling control cause or a combination of the driving behavior and the traveling control cause; characterized in that a discomfort index in which the discomfort felt by the occupant is indexed is retained in association with the combination of the traveling control content and the traveling control cause, an output determination threshold which is a standard value regarding whether to output information based on the discomfort is set in the discomfort index, and the traveling control discomfort determination unit causes the traveling control information output unit to output the traveling control content and the specified traveling control cause in a case in which the traveling control discomfort determination unit determines that the discomfort index exceeds the threshold. an externality recognition information acquisition unit that receives externality recognition information from an externality sensor ascertaining target objects outside the self-vehicle including an obstacle and another vehicle on a route or receives information from a road side through out-of-vehicle communication to acquire the externality recognition information; a driving behavior decision unit that decides driving behavior content to be taken by the self-vehicle based on the externality recognition information received from the externality recognition information acquisition unit and self-vehicle information which is information including a position and a traveling speed of the self-vehicle; a driving behavior cause specifying unit that specifies a driving behavior cause as a reason why the driving behavior content received from the driving behavior decision unit is decided; a driving behavior information output unit that outputs the driving behavior content and the driving behavior cause specified in regard to the driving behavior content; a traveling control content decision unit that decides traveling control content of the vehicle based on a driving behavior decided by the driving behavior decision unit; a traveling control cause specifying unit that specifies a traveling control cause as a reason why the traveling control content is decided; a traveling control information output unit that outputs the traveling control content and the specified traveling control cause; a traveling control discomfort determination unit that determines whether the traveling control gives discomfort to an occupant of the vehicle in regard to a combination of the traveling control content and the traveling control cause or a combination of the driving behavior and the traveling control cause; characterized in that a discomfort index in which the discomfort felt by the occupant is indexed is retained in association with the combination of the traveling control content and the traveling control cause, an output determination threshold which is a standard value regarding whether to output information based on the discomfort is set in the discomfort index, and the traveling control discomfort determination unit causes the traveling control information output unit to output the traveling control content and the specified traveling control cause in a case in which the traveling control discomfort determination unit determines that the discomfort index exceeds the threshold.