In order to prevent an occurrence of dieseling phenomenon, and to prevent engine rotation speed from decreasing during idle operation or the idle operation from being stopped, in step S111, it is determined whether the flag value of an idle stop flag F_IDLSTP is “1” or not. If it is determined that the determination result is “YES”, that is, if it is determined that the internal combustion engine body is stopped, 0% is set to a target purge control valve drive duty value PGCMD (step S105), and 0 is set to the target purge flow rate QPGC (step S106). If it is determined that the determination result is “NO”, that is, when the internal combustion engine body is in operation, PGCMD calculation processing is executed (step S112). While the internal combustion engine body is stopped, execution of purge is stopped, thereby an occurrence of a dieseling phenomenon which is caused because the flow rate of the air flowing into the internal combustion engine body increases and the air is compressed, is prevented, thereby suppressing vibration from occurring in the internal combustion engine body.