PURPOSE: To provide a dressing device which can get rid of danger experienced by manual operations when dressing is carried out without assistance, and is also free of skill and fatigue.

CONSTITUTION: In a dressing device for a grinding wheel mounted on a grinding machine which carries out chamfering and angle cutting for the four peripheral sides of a thin pane of glass cut into a square or a rectangle, the device is provided with an air chuck 32 arresting a tool 27 which dresses the clogged groove (a) of a grinding wheel 25 after chamfering and angle cutting for the thin pane of glass has been over. And the device is made up of an air cylinder 34 which pushes the aforesaid tool 27 onto the groove (a) of the grinding wheel 25 every set time for the set period of time via the air chuck 32, a tool setting table 37 which is moved for the alignment of the groove (a) position of the grinding wheel 25 when the tool is arrested by the air chuck 32, and of a means provided for the grinding machine which shifts its position to each groove (a) and (b) of a plural number of the grinding wheels 25 while being aligned with the position of the tool 27 arrested by the air chuck 32.