PURPOSE: To form a spiral pattern of paint on the surface of a glass bottle by setting a spray nozzle of a spray gun having a sharp diffusion angle of a paint toward the peripheral surface of a glass bottle, turning the glass bottle and moving the spray nozzle simultaneously along the direction parallel to the turning axis of the glass bottle.

CONSTITUTION: A spray nozzle of a spray gun 2 having a sharp diffusion angle of a paint is set at an appropriate distance from the peripheral surface of a glass bottle 1 to direct to the surface of the bottle 1. The glass bottle 1 is turned around its central axis, and a paint is sprayed onto the surface of the glass bottle 1 while moving the nozzle of the spray gun 2 in the parallel direction to the central axis of turning of the glass bottle 1. In this way, a linear spiral pattern is easily formed on the periphery of the glass bottle 1. Several spiral patterns may be formed if the moving speed of the spray gun 2 and the turning speed of the glass bottle are varied.