本文使用美國職棒大聯盟球員資料，分析職業球員在合約年時是否會付出額外努力使成績提升，以獲得高額複數年合約。然而，在合約到期後方簽訂新合約的自由球員及薪資仲裁球員；與合約到期前提前獲得新合約的延長合約球員，在簽約前後的表現或許有所差異。過往文獻中僅分析球員在合約年是否存在合約年效果，卻未能針對不同簽約方式的合約年效果進行比較。本研究利用美國職棒大聯盟2000年至2013年296名野手的合約資料與成績表現，探討以不同合約方式簽約的球員在合約年效果上的區別。實證結果顯示，明確得知球季結束後將簽訂新合約的自由球員與薪資仲裁球員在合約年表現顯著較佳。而延長合約球員在新約簽訂後的績效表現並無顯著差異。;This thesis analyses whether a baseball player pays additional effort to obtain a multiple year contract. The existing literature has mainly focused on examining the contract-year effect for free agent players. However, the behavior of players who are qualified for salary arbitration or who have been offered extension contracts is also worth studying. As a result, this study uses 296 MLB player’s data between 2000 and 2013 to explore whether different contract type will lead to different contract-year effect. The results show that free agent and salary arbitration players perform significantly better during the contract year. However, the performances of players with extension contracts are relatively stable during the year they are provided with the extension contracts.