PURPOSE: To attain automation by mounting a grease injecting gun to a lubricating port which is provided on a chock based on startup command by the scheduled program of operation after a roll is placed on the receiving base of a roll transporting truck and executing lubrication based on lubrication command.

CONSTITUTION: A grease storage tank 3, grease piping 6 from that tank and grease injecting gun 5 which is freely moved in and out of the tip of the grease piping are provided to the roll transporting truck 1. A lubricating device between the inside of the inner race of bearing which is provided with a sequencer with which the start-up command for moving that grease injecting gun in and out and discharging grease from the grease storage tank are output and the journal parts of roll is provided. In this way, lubrication into the chock of roll for rolling mill is automatically executed during roll transportation, perfect unattended operation is attained and time for supplying roll to the rolling mill can be shortened.