A shock absorbing device includes a cylinder. A partition wall member is inserted into the cylinder to be free to slide and partitions an interior of the cylinder into two operating chambers. A passage connects the two operating chambers. A free piston is inserted into a pressure chamber to be free to slide and partitions the pressure chamber into one chamber that communicates with one operating chamber via a one side flow passage and another chamber that communicates with the other operating chamber via another side flow passage. A spring element generates a biasing force for suppressing displacement of the free piston relative to the pressure chamber. One or both of a bypass flow passage that connects the other chamber and the one operating chamber and a bypass flow passage that connects the one chamber and the other operating chamber is provided. A relief valve is provided in the bypass flow passage.