The invention belongs to the technical field of detection control and particularly provides an automatic garage parking space detection device based on the piezoelectric effect. The automatic garage parking space detection device comprises a gravity sensor (1), a wireless transceiving module a (2), a wireless transceiving module b (3), a controller (4) and a displayer (5). The gravity sensor (1), the wireless transceiving module a (2), the wireless transceiving module b (3), the controller (4) and the displayer (5) are all low-power-consumption devices. According to the automatic garage parking space detection device, the gravity sensor is used for accurately measuring the parking conditions of different parking spaces, conducting statistics on the number of idle parking spaces in a garage and transmitting the number of the idle parking spaces to an entrance through the wireless transceiving module a for displaying so that car owners can be guided to park cars conveniently. The automatic garage parking space detection device has the advantages of being accurate in measuring and displaying, simple in structure, low in cost, efficient and practical, and greatly improves the management efficiency and level of the garage.