The present invention relates to an apparatus for sensing and controlling an amount of gas supply and a method for sensing and controlling an amount of gas supply thereby, which can sense a supply amount of the corresponding gas from an optical sensor in real time on the basis of the number of bubbles generated by any set time difference at the time when a target gas flows in a tube in order to differentiate the supply amount more accurately and whether or not the gas supply state is bad, and which can control pressure of the tube in real time by a series of automated devices in order to precisely realize the target supply amount according to gas supply information obtained from the optical sensor, thereby positively preventing malfunction and continuously maintaining the initial set amount of gas supply.