An air tool with a modularized air pad includes several air pad units, each of which has one pad body whose top surface is formed with an accommodating recess and whose one side has an air opening; two air bags disposed at the bottom of the accommodating recess, each of the air bags having two air chambers and connecting to the air opening via an air pipe; and one buffer pad accommodated in the accommodating recess on the air bags. When the air opening is selected to inflate the air chamber of one air bag, the buffer pad undergoes an upward swing motion according to the inflated air bags.