To provide a guide device for a parking lot capable of suppressing the capacity of data to be transmitted to and received from other vehicles to a low value, and creating map data of high accuracy irrespective of the number of vehicles parked in the parking lot or the like.

The guide device for the parking lot is provided with: a map data creation part 51 for creating map data in the parking lot on the basis of travel route data of its own vehicle from its entry position into the parking lot up to its parking position or from the parked position up to its way out position, when its entry into the parking lot is detected; a transmission processing part 52 for transmitting the created map data and/or parked position data of the own vehicle to other vehicles through a wireless communication device 31 as parking information; and a receiving processing part 53 for receiving parking information transmitted from other vehicles through the communication device 31. The creation part 51 is so configured as to perform update processing of map data based on the parking information received by the receiving part 53, and the transmission part 52 is so configured as to transmit the map data updated by the creation part 51 to the other vehicles.