According to the pilot, following a night visual flight rules cross-country flight, he overflew the destination airport at 1,500 ft above ground level and set up a normal approach. Just before touchdown, he saw a deer walk onto the runway from the right and collide with the left main landing gear, which then separated from the airplane. As the airplane settled, the left wing struck the runway, and the airplane veered left. The airplane exited the left side of the runway and collided with a drainage culvert. The airplane sustained substantial damage the left wing spar and the left main landing gear attachment points. The airport facility directory did not contain a note to caution that deer were in the vicinity of the airport. The pilot reported that there were no mechanical malfunctions or failures with the airplane that would have precluded normal operation.