Small Punch (SP) Creep test is a new semi destructive testing methodology where a very small specimen is required to examine creep properties. The size and the volume of SP creep specimens are much smaller than those of conventional uniaxial creep specimens. This testing methodology has been recognized as a practical procedure to know residual creep lives of high temperature components. Employing a part of aged boiler tubes made of STBA24 used for about 140,000 hours below 500°C, the SP and the uniaxial creep tests were conducted at 650°C in air and Argon gas to study the relationship between the SP and the uniaxial creep tests, and to investigate the influence of testing atmosphere on test results. SP creep rupture lives were nearly the same regardless of both sampling area and the testing atmosphere. Ratio of an applied load in the SP creep test to an initial stress in the uniaxial one was about 2.1mm², and a little increased with the rupture life.