An image forming apparatus, a host apparatus, and an encryption method for print data, the method of encrypting the print data of the host apparatus connected to the image forming apparatus including: displaying an encryption setting screen for the print data; selecting an encryption logic to encrypt the print data through the encryption setting screen; converting the print data according to the selected encryption logic; and transmitting the converted print data to the image forming apparatus. Accordingly, the print data is encrypted and decrypted on the basis of the selected encryption logic and corresponding decryption logic set up according to users, thereby increasing security.