Abstract: A flow controller and a flow controlling method are adapted to be released from conventional restrictions by using a novel type called a pulse shot type. A pulse shot (opening/closing operation of a first cutoff valve (12) and, after that, opening/closing operation of a second cutoff valve (17)) is repeated. Simultaneously, a volume flow Q of process gas exhausted from the second cutoff valve (17) per unit time on the basis of after-filling pressure and after-exhaust pressure of the process gas in a gas filling capacity (13) measure by a pressure sensor (14). Furthermore, a mode of the pulse shot is changed to control the volume flow Q of the process gas exhausted from the second cutoff valve (17) per unit time.