Abstract: An image printing apparatus according to the present invention, includes a unit for conveying a printing medium and a unit for scanning a carriage to move across the direction in which the printing medium is conveyed by the printing medium conveying unit, the carriage being attached with a printing head for printing an image on the printing medium, the image printing apparatus further comprises a scale disposing along the direction of scanning of the carriage by the scanning unit, a sensor for detecting the position of the carriage to the scale, the sensor being mounted on the carriage opposing to the scale, and a cover for covering the sensor and at least a part of the scale adjoining the sensor, the cover including ribs 41a and 41b for guiding the scale to predetermined position with respect to the sensor, thereby resolving the problem that the printing of high-quality image on the printing medium is hindered by the foreign matters such as the paper dust, common dust, mist and the like adhering to the surfa