A monitoring device for a fuel injection quantity control device, the fuel injection quantity control device including an injector configured to inject a fuel supplied to an engine and a control unit configured to i) drive the injector, ii) calculate an injection quantity command value as an amount of the fuel required to be injected from the injector in one cycle based on an engine operation state, iii) execute the injection of the fuel equivalent in amount to the injection quantity command value by energization of the injector such that the fuel injection is divided into a main injection and a sub injection and executed, the sub injection being the injection of the fuel smaller in amount than the main injection, and iv) add an individual difference correction that is attributable to an individual difference between the injectors to each of the energization time command values and add a micro-injection correction to an energization time command value for the injector for performing the sub injection, the monitoring device characterized by an electronic control unit configured to i) calculate monitor injection quantities as amounts of the fuel actually injected by the main injection and the sub injection based on an energization time monitor value of the injector for each of the main injection and the sub injection, ii) execute a correction processing for the monitor injection quantity such that: the amount of the micro-injection correction and the amount of an individual difference correction are removed from the monitor injection quantity, by subtracting the micro-injection correction and the individual difference correction from the energization time monitor value for recalculation of the monitor injection quantity, when the monitor injection quantity is below a determined determination value, wherein the removal of the micro-injection correction amount from the monitor injection quantity is not performed when the monitor injection quantity is equal to or larger than the determination value, and the removal of the individual difference correction amount is performed when the monitor injection quantity is equal to or larger than the determination value, and iii) determine a presence or absence of an abnormality of the fuel injection quantity control device based on a comparison between a total value of the monitor injection quantities after the correction processing in the one cycle of the engine and the injection quantity command value. i) calculate monitor injection quantities as amounts of the fuel actually injected by the main injection and the sub injection based on an energization time monitor value of the injector for each of the main injection and the sub injection, ii) execute a correction processing for the monitor injection quantity such that: the amount of the micro-injection correction and the amount of an individual difference correction are removed from the monitor injection quantity, by subtracting the micro-injection correction and the individual difference correction from the energization time monitor value for recalculation of the monitor injection quantity, when the monitor injection quantity is below a determined determination value, wherein the removal of the micro-injection correction amount from the monitor injection quantity is not performed when the monitor injection quantity is equal to or larger than the determination value, and the removal of the individual difference correction amount is performed when the monitor injection quantity is equal to or larger than the determination value, and the amount of the micro-injection correction and the amount of an individual difference correction are removed from the monitor injection quantity, by subtracting the micro-injection correction and the individual difference correction from the energization time monitor value for recalculation of the monitor injection quantity, when the monitor injection quantity is below a determined determination value, wherein the removal of the micro-injection correction amount from the monitor injection quantity is not performed when the monitor injection quantity is equal to or larger than the determination value, and the removal of the individual difference correction amount is performed when the monitor injection quantity is equal to or larger than the determination value, and iii) determine a presence or absence of an abnormality of the fuel injection quantity control device based on a comparison between a total value of the monitor injection quantities after the correction processing in the one cycle of the engine and the injection quantity command value.