A behavior sensing device includes: a processor configured to: acquire sensor data from one or more sensors； calculate a first characteristic amount serving as an index of characteristic of biological reaction to a behavior to be sensed from the sensor data； calculate a probability of occurrence of the behavior as a first behavior occurrence probability from the first characteristic amount； calculate a second characteristic amount serving as another index of characteristic of a habit relating to the behavior to be sensed from the sensor data； calculate another probability of occurrence of the behavior as a second behavior occurrence probability from the second characteristic amount； and determine whether specific behavior is performed based on the first behavior occurrence probability and the second behavior occurrence probability.
