An I/O module unit comprising: an I/O unit (Un) configured to be connected to input devices and to acquire input data from the input devices used as sensors arranged on a control object apparatus used in a factory; a controller configured to control the I/O unit; and an I/O allocation management apparatus configured to be connected to the I/O unit (Un) and the controller and to manage the I/O unit (Un), wherein the I/O allocation management apparatus comprises: an I/O management information storing part, storing: a unit operation setting, indicating a relation between input data acquired and transferred from the input devices by the I/O unit (Un) and a setting value related to the input data, and an I/O allocation setting, indicating a relation between the input data and specification information that specifies a storage area, wherein the storage area is within a plurality of storage areas included in a storage part of a transfer destination to which the input data is transferred by the I/O unit (Un) and is allocated as the transfer destination of the input data; and an allocation management part (41 adapted, when the setting value is changed in the unit operation setting, to specify, based on the changed setting value, a storage capacity required for a storage of the input data generated along with the change of the setting value, and to judge whether a mismatch occurs in an allocation state between the required storage capacity of the input data and the storage area specified in the I/O allocation setting and allocated before the change of the setting value; wherein the I/O module unit is adapted to inform a user of the judgment result. an I/O unit (Un) configured to be connected to input devices and to acquire input data from the input devices used as sensors arranged on a control object apparatus used in a factory; a controller configured to control the I/O unit; and an I/O allocation management apparatus configured to be connected to the I/O unit (Un) and the controller and to manage the I/O unit (Un), wherein the I/O allocation management apparatus comprises: an I/O management information storing part, storing: a unit operation setting, indicating a relation between input data acquired and transferred from the input devices by the I/O unit (Un) and a setting value related to the input data, and an I/O allocation setting, indicating a relation between the input data and specification information that specifies a storage area, wherein the storage area is within a plurality of storage areas included in a storage part of a transfer destination to which the input data is transferred by the I/O unit (Un) and is allocated as the transfer destination of the input data; and an allocation management part (41 adapted, when the setting value is changed in the unit operation setting, to specify, based on the changed setting value, a storage capacity required for a storage of the input data generated along with the change of the setting value, and to judge whether a mismatch occurs in an allocation state between the required storage capacity of the input data and the storage area specified in the I/O allocation setting and allocated before the change of the setting value; wherein the I/O module unit is adapted to inform a user of the judgment result. an I/O management information storing part, storing: a unit operation setting, indicating a relation between input data acquired and transferred from the input devices by the I/O unit (Un) and a setting value related to the input data, and an I/O allocation setting, indicating a relation between the input data and specification information that specifies a storage area, wherein the storage area is within a plurality of storage areas included in a storage part of a transfer destination to which the input data is transferred by the I/O unit (Un) and is allocated as the transfer destination of the input data; and a unit operation setting, indicating a relation between input data acquired and transferred from the input devices by the I/O unit (Un) and a setting value related to the input data, and an I/O allocation setting, indicating a relation between the input data and specification information that specifies a storage area, wherein the storage area is within a plurality of storage areas included in a storage part of a transfer destination to which the input data is transferred by the I/O unit (Un) and is allocated as the transfer destination of the input data; and an allocation management part (41 adapted, when the setting value is changed in the unit operation setting, to specify, based on the changed setting value, a storage capacity required for a storage of the input data generated along with the change of the setting value, and to judge whether a mismatch occurs in an allocation state between the required storage capacity of the input data and the storage area specified in the I/O allocation setting and allocated before the change of the setting value; wherein the I/O module unit is adapted to inform a user of the judgment result.