A substrate production line monitoring device comprising: a defect indication detection unit that is configured to detect an indication of a production defect of a substrate production line; and a defect cause identification unit that is configured to identify a cause of the production defect, wherein the defect indication detection unit is configured to collect measurement information that is measured by an inspection apparatus for each reference (REF1, REF2, REF3) that identifies a position on substrates (PB1, PB2, PB3) for a plurality of substrates in the order of production, and is configured to detect an indication of the production defect from the change with time of the measurement information at the references (REF1, REF2, REF3), wherein the defect indication detection unit is configured to detect the indication of the production defect on the basis of a process capability index that is calculated from the measurement information, and is configured to determine whether or not the process capability index is in a standard range, and wherein, when the defect indication detection unit detects an indication of a production defect at a reference (REF1, REF2, REF3), the defect indication detection unit is configured to turn on a production defect determination flag, wherein the defect cause identification unit is configured to perform stratified analysis on the basis of production information that is related to the reference (REF1, REF2, REF3) at which the production defect determination flag is turned on when the defect indication detection unit detects the indication of the production defect, so that an object, which is to be analyzed, is limited to the production information related to the reference (REF1, REF2, REF3) at which an indication of the production defect is detected, characterized in that the defect cause identification unit is configured to identify a cause of the production defect from a result of the analysis, wherein a specific procedure for identifying a cause of a production defect is the same as the procedure for detecting an indication of a production defect, and comprises calculating a process capability index from the production information related to the reference (REF1, REF2, REF3) at which an indication of the production defect is detected and determining whether said process capability index is in a standard range. a defect indication detection unit that is configured to detect an indication of a production defect of a substrate production line; and a defect cause identification unit that is configured to identify a cause of the production defect, wherein the defect indication detection unit is configured to collect measurement information that is measured by an inspection apparatus for each reference (REF1, REF2, REF3) that identifies a position on substrates (PB1, PB2, PB3) for a plurality of substrates in the order of production, and is configured to detect an indication of the production defect from the change with time of the measurement information at the references (REF1, REF2, REF3), wherein the defect indication detection unit is configured to detect the indication of the production defect on the basis of a process capability index that is calculated from the measurement information, and is configured to determine whether or not the process capability index is in a standard range, and wherein, when the defect indication detection unit detects an indication of a production defect at a reference (REF1, REF2, REF3), the defect indication detection unit is configured to turn on a production defect determination flag, wherein the defect cause identification unit is configured to perform stratified analysis on the basis of production information that is related to the reference (REF1, REF2, REF3) at which the production defect determination flag is turned on when the defect indication detection unit detects the indication of the production defect, so that an object, which is to be analyzed, is limited to the production information related to the reference (REF1, REF2, REF3) at which an indication of the production defect is detected, characterized in that the defect cause identification unit is configured to identify a cause of the production defect from a result of the analysis, wherein a specific procedure for identifying a cause of a production defect is the same as the procedure for detecting an indication of a production defect, and comprises calculating a process capability index from the production information related to the reference (REF1, REF2, REF3) at which an indication of the production defect is detected and determining whether said process capability index is in a standard range.