A flow meter device including: plural fluid passages which are provided between an inlet section into which a fluid flows and an outlet section from which the fluid flows out, and through which the fluid flows; plural flow value measuring units (M1 to Mn) installed in the plural fluid passages, respectively, and configured to measure flow values of the fluid flowing through the fluid passages, respectively; a calculation unit configured to derive total flow values of the fluid flowing through the flow meter device, each total flow value based respectively on the flow value measured by any one of the flow value measuring units (M1 to Mn) included in at least two fluid passages of the plural fluid passages; and a control unit configured to, when the control unit determines that at least one of the total flow values derived by the calculation unit is smaller than a first predetermined value, cause one or more of the plural flow value measuring units (M1 to Mn) to stop a measuring operation of the flow value, and decide as a monitoring measuring unit the flow value measuring unit (M1 to Mn) which is other than the one or more of the plural flow value measuring units (M1 to Mn) and is activated to perform the measuring operation of the flow value; wherein the control unit is further configured to, when the flow value measuring unit (M1 to Mn) decided as the monitoring measuring unit is activated to perform the measuring operation of the flow value, determine whether or not to cause the one or more of the plural flow value measuring units (M1 to Mn) to resume the measuring operation of the flow value, based on whether or not the flow value measured by the monitoring measuring unit is larger than a second predetermined value. plural fluid passages which are provided between an inlet section into which a fluid flows and an outlet section from which the fluid flows out, and through which the fluid flows; plural flow value measuring units (M1 to Mn) installed in the plural fluid passages, respectively, and configured to measure flow values of the fluid flowing through the fluid passages, respectively; a calculation unit configured to derive total flow values of the fluid flowing through the flow meter device, each total flow value based respectively on the flow value measured by any one of the flow value measuring units (M1 to Mn) included in at least two fluid passages of the plural fluid passages; and a control unit configured to, when the control unit determines that at least one of the total flow values derived by the calculation unit is smaller than a first predetermined value, cause one or more of the plural flow value measuring units (M1 to Mn) to stop a measuring operation of the flow value, and decide as a monitoring measuring unit the flow value measuring unit (M1 to Mn) which is other than the one or more of the plural flow value measuring units (M1 to Mn) and is activated to perform the measuring operation of the flow value; wherein the control unit is further configured to, when the flow value measuring unit (M1 to Mn) decided as the monitoring measuring unit is activated to perform the measuring operation of the flow value, determine whether or not to cause the one or more of the plural flow value measuring units (M1 to Mn) to resume the measuring operation of the flow value, based on whether or not the flow value measured by the monitoring measuring unit is larger than a second predetermined value.