An image processing apparatus comprising: an image forming unit configured to print an image on a sheet with an electrophotographic method, wherein the image forming unit includes an image carrier (311,321,331,341) on which an electrostatic latent image is formed; a detection processing unit configured to detect a streaky image along a sub-scanning direction from a first image (X11, X12, X13, X14) and a second image (X21, X22, X23, X24) among images indicated by image data, wherein the first image and the second image are images printed on the sheet, the first image (X11, X12, X13, X14) having a print density equal to or more than a predetermined reference print-density value, and the second image (X21, X22, X23, X24) having a print density less than the reference print-density value; and a determination processing unit configured to determine a cause of abnormality in the image forming unit based on a detection result of the streaky image by the detection processing unit for each of the first image (X11, X12, X13, X14) and the second image (X21, X22, X23, X24), wherein the detection processing unit is configured to detect a gradient of a print density transition in an outer circumference of the streaky image; the determination processing unit is configured to determine the cause of abnormality based on presence or absence of the streaky image detected in each of the first image (X11, X12, X13, X14) and the second image (X21, X22, X23, X24) and the gradient of the print density transition in the outer circumference of the streaky image; characterized in that the determination processing unit is configured to identify the image carrier (311,321,331,341) as the cause of abnormality when the detection processing unit detects the streaky image in only the second image (X21, X22, X23, X24) and the gradient of the print density transition is equal to or more than a predetermined threshold value. an image forming unit configured to print an image on a sheet with an electrophotographic method, wherein the image forming unit includes an image carrier (311,321,331,341) on which an electrostatic latent image is formed; a detection processing unit configured to detect a streaky image along a sub-scanning direction from a first image (X11, X12, X13, X14) and a second image (X21, X22, X23, X24) among images indicated by image data, wherein the first image and the second image are images printed on the sheet, the first image (X11, X12, X13, X14) having a print density equal to or more than a predetermined reference print-density value, and the second image (X21, X22, X23, X24) having a print density less than the reference print-density value; and a determination processing unit configured to determine a cause of abnormality in the image forming unit based on a detection result of the streaky image by the detection processing unit for each of the first image (X11, X12, X13, X14) and the second image (X21, X22, X23, X24), wherein the detection processing unit is configured to detect a gradient of a print density transition in an outer circumference of the streaky image; the determination processing unit is configured to determine the cause of abnormality based on presence or absence of the streaky image detected in each of the first image (X11, X12, X13, X14) and the second image (X21, X22, X23, X24) and the gradient of the print density transition in the outer circumference of the streaky image; characterized in that the determination processing unit is configured to identify the image carrier (311,321,331,341) as the cause of abnormality when the detection processing unit detects the streaky image in only the second image (X21, X22, X23, X24) and the gradient of the print density transition is equal to or more than a predetermined threshold value.