A parking assistance device (14, 14a, 30) comprising: a situation information acquisition unit configured to, when a vehicle is repeatedly parked at a same parking target position, acquire peripheral situation information of a peripheral region including the parking target position detected by a detection unit (15, 15a to 15d, 16, 16a to 16d, 17, 17a to 17h) provided in the vehicle; a storage control unit configured to store first situation information indicating the peripheral situation information and a movement route for reaching the parking target position, which are acquired when the vehicle completes the parking at the parking target position; an information updating unit configured to compare the first situation information with second situation information which indicates the peripheral situation information acquired when the vehicle newly parks at the parking target position, to determine, based on said comparison, whether new information which is not included in the first situation information is included in the second situation information and whether a region specified by the new information does not interfere with a region where the movement route exists, and to, in a case where the region specified by the new information does not interfere with a region where the movement route exists, update the first situation information by the second situation information which includes the new information; a current position estimation unit configured to estimate a current position of the vehicle by comparing the first situation information with the second situation information; and a guidance control unit configured to guide the vehicle to the parking target position according to the estimated current position and the movement route. a situation information acquisition unit configured to, when a vehicle is repeatedly parked at a same parking target position, acquire peripheral situation information of a peripheral region including the parking target position detected by a detection unit (15, 15a to 15d, 16, 16a to 16d, 17, 17a to 17h) provided in the vehicle; a storage control unit configured to store first situation information indicating the peripheral situation information and a movement route for reaching the parking target position, which are acquired when the vehicle completes the parking at the parking target position; an information updating unit configured to compare the first situation information with second situation information which indicates the peripheral situation information acquired when the vehicle newly parks at the parking target position, to determine, based on said comparison, whether new information which is not included in the first situation information is included in the second situation information and whether a region specified by the new information does not interfere with a region where the movement route exists, and to, in a case where the region specified by the new information does not interfere with a region where the movement route exists, update the first situation information by the second situation information which includes the new information; a current position estimation unit configured to estimate a current position of the vehicle by comparing the first situation information with the second situation information; and a guidance control unit configured to guide the vehicle to the parking target position according to the estimated current position and the movement route.