A manufacturing method of electrochromic devices (10) includes the steps of providing a first and second sheet including a first (22) and second (24) plastic substrate, respectively, at least partially coated with a first (12) and second (14) electron conducting layer, respectively. The first sheet is at least partially coated with a first electrochromic layer (16). The second sheet is at least partially coated with a counter electrode layer (18). The first and second sheets are laminated with an electrolyte layer (20) interposed in-between into an electrochromic laminate sheet (30). The electrochromic device is at least partially defined by forming a seal (50) through the electrochromic laminate sheet (30) at a distance (D) from a peripheral edge (31). The distance (D) is preferably larger than the mean diffusion lengths of oxygen, water or an electrolyte component in the electrolyte during a predetermined time period.