To provide an image forming apparatus capable of installing external applications and adding various functions.

This image forming apparatus provides a user service for image forming processing and is provided with a large-capacity storage device (HDD 103), capable of storing an external application 117 for providing the user service, a PC card interface part 230 for reading the external application 117 from an insertable and extractable PC card 240 for storing the external application 117 in an installable form in the image forming apparatus, and an installer 118 for installing the external application 117 from the PC card 240 to the large-capacity storage device (HDD 103).