The present invention relates to a door stopper (10) comprising a dampening piston (30), a pin holder (40) provided at the piston end (32) of the piston shaft (31) of the dampening piston (30), and a spring (56) connected to the pin holder (40), in order to decelerate the sliding door during opening thereof in vehicles having sliding door and in order to reduce the hitting effect. As an improvement, the present invention is characterized by comprising a first roller (60) and a second roller (70) connected to each other so as to rotate together in a coaxial manner, and a first rope (61) connected to the pin holder (40) from one end and connected to the first roller (60) from the other end and a second rope (71) connected to the spring (56) from one end and connected to the second roller (70) from the other end, and further characterized in that the first roller (60) is greater than the second roller (70).