WITH t AS ( SELECT '201501' yw FROM dual UNION ALL SELECT '201652' FROM dual UNION ALL SELECT '201701' FROM dual UNION ALL SELECT '201801' FROM dual UNION ALL SELECT '201806' FROM dual ) SELECT yw , TO_CHAR( TRUNC(NEXT_DAY(TO_DATE(SUBSTR(yw, 1, 4)||'01', 'yyyymm')-1, 5), 'iw') --1주차월요일 + SUBSTR(yw, 5, 2) * 7 - 7 -- 주차 만큼 일자 더하기 , 'yyyymmdd') ymd FROM t ;