This paper describcs ai ユ initiaI shape − finding problem for a gas − in冂atablercHector . The probleln is formulated as a problen ユ fQr 加 ding an init 工 al mernbrane shape wh se deformed shape under prescribed pressure becomes a parabol 〔 }id of revoluti (m . The initial shape is described by the even − order power series of the radia 亙 co rdinate variable . The deformed shape is analyzed by using the fin瓦c element method . Furthermore , thc prototype with the initial shape that is determhned frQm the numerical 匚alculation result is produced and the deforrned shape is measured . The effectiveness of the initial shape is confirmed from the experimental res し11t.