A door locking device with an antitheft mechanism comprises a main lock lever linked to a key cylinder and changed over from an unlock position to an antitheft position through a lock position, a sub lock lever linked to an inside lock button of the door and changed over to an unlock position and a lock position, and a linkage member having sufficient elasticity to connect the lock levers with each other between the lock position and unlock position. As the main lock lever is displaced from the lock position to the antitheft position the linkage member is elastically deformed and permits the sub lock lever to be left at the lock position, and as the main lock lever is displaced to the antitheft position the sub lock lever is composed so that it can not change over the main lock lever.