A marking device includes an ink jet printer (6) using an on-demand system. The printer (6) includes a body (18), a head (22), a slide table (24), a tray (26), an ink vessel (28), a solvent vessel (30), a pump (32) and a rest (34). The head (22) has a nozzle. The shortest distance between the tip of the nozzle and a golf ball (46) set into the tray (26) is equal to or greater than 0.2 mm. The ink vessel (28) is filled with an oil-based ink or an ultraviolet setting type ink. The ink is fed to the head (22) through a tube (48). The ink is discharged from the nozzle and is then moved to the surface of the golf ball (46). The solvent is supplied from the solvent vessel (30) toward the rest (34) through a tube (50) and the pump (32). When the printer (6) is stopped, the nozzle is immersed in the solvent of the rest (34).