The judgment below is reversed and the case is remanded to Seoul High Court.

The grounds of appeal are examined.

1. In light of Articles 49 subparag. 2, 54(1), and 67(1) and (5) of the former National Pension Act (amended by Act No. 11143, Dec. 31, 201; hereinafter the same shall apply), Article 46 of the former Enforcement Decree of the National Pension Act (amended by Presidential Decree No. 2359, Dec. 8, 201; hereinafter the same shall apply), and attached Table 2 of the former Enforcement Decree of the National Pension Act (amended by Presidential Decree No. 23359, Dec. 8, 2011; hereinafter the same shall apply), a disability pension under the National Pension Act is paid to a person who has a physical or mental disability even after completion of treatment due to a disease or injury incurred during the subscription to the National Pension, and there is a cause for payment of a disability pension after the completion of treatment.

Therefore, the decision to pay a disability pension shall be based on the law at the time when the right to claim the payment of the disability pension is acquired, that is, the right to claim the payment of the disability pension.

Furthermore, this legal doctrine also applies to cases where disability pension amount is modified and paid as a result of a change in the existing disability grade. As such, the determination of disability grade should be based on the law of “the date on which a disease or injury is completely cured,” which is the base date for the assessment of disability grade again.

2.(a)

According to Article 67(1) and (2) of the former National Pension Act and Article 46(4) of the former Enforcement Decree of the National Pension Act, the National Pension Disability Examination Regulations (amended by the Ministry of Health and Welfare No. 2006-47, Jun. 14, 2006; hereinafter “existing Public Notice”) stipulating the criteria for determining the degree of disability according to delegation of the authority under Article 67(1) and (2) of the former National Pension Act, if a person who is not entitled to a disability pension is not completely cured even after one year and six months from the date of completion of treatment, (2) if the person is completely cured after one year and six months from the date of initial diagnosis, he/she shall be subject to a disability pension before he/she reaches the age of 60