To provide an image formation device which does not produce a gap in the writing starting-position of main scanning even if the quantity of light of light beam varies according to pixel density.

The image formation device is equipped with a 1/K divider 55 for dividing a standard high-frequency clock into a clock of frequency corresponding to the pixel density, a synchronous sense pulse-width counter 60 for measuring the pulse width of synchronous sense signal, an internal synchronous signal formation section 56 for forming the internal synchronous signal by correcting the synchronous sense signal, a main-scanning counter 58 for counting a pixel clock on the basis of the internal synchronous signal which has been formed in the internal synchronous signal formation section 56 and a main-scanning resist adjustment means for adjusting the writing starting-position of main scanning according to the value of the main scanning counter 58.