An image forming device determines the replacement time of components depending on environment. The image forming device includes an engine part performing the printing job using a certain component upon receiving the print command, a printout counter counting the actual number of the printed sheets, an environment detector detecting a certain environmental information by checking status of each component, a memory containing the maximum number of the printable sheets of the component, and a controller driving the component by reading out the operating condition from the memory corresponding to the received environmental information and determining the replacement time of the component by determining the total number of the printed sheets by differentially compensating and accumulating the counted number of the printed sheets depending on the environmental information, and comparing with the maximum number of the printable sheets. Accordingly, accurate replacement time of the component can be estimated.