To provide a color image forming position adjusting device by which a color image forming position and the adjustment of density are accurately performed.

As for the five patches 74 to 78 of a test printing pattern for adjusting positional deviation in an X direction stored in a storage device; the pattern (m) of magenta (M) being an adjusted color is successively shifted by one dot with respect to the pattern (k) of black (K), that is, by two dots in a negative X direction in the case of the patch 74 on the left side, by one dot in the negative X direction in the case of the patch 75, by zero dot in the case of the patch 76, by one dot in a positive X direction in the case of the patch 77 and by two dots in the positive X direction in the case of the patch 78. By printing and outputting the patches, the density of the patch is changed in accordance with the positional deviation of a printing device. The change is detected by a near infrared regular reflection type toner density sensor, and the printing condition is corrected so as to fit to the printing output condition of the patch whose density is the thickest. The same processing is performed to the five pattern patches 81 to 85 of a test printing pattern for adjusting positional deviation in a Y direction.