To provide a determination device, a determination method, and a determination program that shorten a time for determining whether frequency sharing is possible by sensing a radio signal that is primarily used in a region that is secondarily used.SOLUTION: A frequency sharing determination device determines an intersection included in an interference area which is a service area of a primary user as a sensing point from among intersections between a loop with a predetermined interval centered on an installation position of a device that transmits a wireless signal of a secondary user or a contour line of an estimated secondary user wireless signal reception level, and a radiation at predetermined angular intervals extending radially from the center, and determines that a frequency of a wireless signal that is being used primarily can be used secondarily when a ratio of a reception level of the secondary user estimated for each sensing point to a reception level of the primary user measured for each sensing point is less than or equal to a predetermined determination threshold at all the sensing points.SELECTED DRAWING: Figure 5