A passive-type exercising device and its control device are provided in which accuracy of deriving exercise intensity is improved. The passive-type exercising device includes an exercise assistance mechanism for assisting exercise of a user; a load setting value acquisition unit 131 for obtaining a load setting value which is a setting value of a degree that the exercise assistance mechanism assists the user's exercise; an assistance load value derivation unit 132 for deriving an assistance load value that the exercise assistance mechanism assists the user's exercise; a sensor value acquisition unit 134 for obtaining a sensor value outputted by a sensor unit 32 provided at the exercise assistance mechanism; a combined load value derivation unit 135 for deriving a combined load value which is a combined value of the assistance load value and an effective load value of the user's active exercise based on the obtained sensor value; and an exercise intensity derivation unit 150 for deriving an exercise intensity indicating the user's exercise intensity based on the effective load value computed as a difference between the assistance load value and the combined load value.