A method for adjusting timings at which a first laser light source (11 A) and a second laser light source emit lights in an image formation apparatus which comprises a plurality of laser light sources including the first laser light source and the second laser light source, wherein the second laser light source is placed so as to be shifted in the main scanning direction in an amount of a predetermined number of pixel(s) from the first laser light source; a scanner for scanning laser lights emitted from the plurality of laser light sources in a main scanning direction, and a light receiving sensor for receiving the laser lights deflected and scanned by the scanner, the method comprising: a first generation process for making the first laser light source emit light in a first scanning period in which scanning is performed by the scanner, and for generating a first signal which is in synchronization with a pixel clock (PXLCLK2) for the second laser light source at timing delayed by pixel clock corresponding to the predetermined number of pixel(s) from the output of the light receiving sensor obtained in the first scanning period; a second generation process for making the second laser light source emit light in a second scanning period after the first scanning period, and for generating a second signal which is in synchronization with a pixel clock (PXLCLK1) for the first laser light source based on an output from the light receiving sensor obtained in the second scanning period; a third generation process for making the second laser light source emit light in a third scanning period in which scanning is performed by the scanner, and for generating a third signal which is in synchronization with the pixel clock (PXLCLK1) for the first laser lights source based on an output from the light receiving sensor obtained in the third scanning period; a fourth generation process for making the first laser light source emit light based on the second signal in a fourth scanning period after the third scanning period, and for generating a fourth signal which is in synchronization with the pixel clock (PXLCLK2) for the second laser light source at timing delayed by pixel clock corresponding to the predetermined number of pixel(s) from an output from the light receiving sensor obtained in the fourth scanning period; and an adjustment process for adjusting, based on a time interval (t1, t2) between the first signal and the second signal and a time interval (t1' and t2') between the second signal and the third signal, a relationship between timings at which the first laser light source and the second laser light source emit lights. a first generation process for making the first laser light source emit light in a first scanning period in which scanning is performed by the scanner, and for generating a first signal which is in synchronization with a pixel clock (PXLCLK2) for the second laser light source at timing delayed by pixel clock corresponding to the predetermined number of pixel(s) from the output of the light receiving sensor obtained in the first scanning period; a second generation process for making the second laser light source emit light in a second scanning period after the first scanning period, and for generating a second signal which is in synchronization with a pixel clock (PXLCLK1) for the first laser light source based on an output from the light receiving sensor obtained in the second scanning period; a third generation process for making the second laser light source emit light in a third scanning period in which scanning is performed by the scanner, and for generating a third signal which is in synchronization with the pixel clock (PXLCLK1) for the first laser lights source based on an output from the light receiving sensor obtained in the third scanning period; a fourth generation process for making the first laser light source emit light based on the second signal in a fourth scanning period after the third scanning period, and for generating a fourth signal which is in synchronization with the pixel clock (PXLCLK2) for the second laser light source at timing delayed by pixel clock corresponding to the predetermined number of pixel(s) from an output from the light receiving sensor obtained in the fourth scanning period; and an adjustment process for adjusting, based on a time interval (t1, t2) between the first signal and the second signal and a time interval (t1' and t2') between the second signal and the third signal, a relationship between timings at which the first laser light source and the second laser light source emit lights.