This paper attempts to show how the confidence game functions in Henry James's The Portrait of a Lady (1881). This attempt is made by analyzing the portrait of Isabel as a dupe, and by studying James's techniques to make the mechanism of the con game run smoothly. This analysis and study seem effective because the character of Isabel holds the key to the development of the con game. Also because James concentrated his own technical faculty on ways to make the con game interesting and convincing, by making her portrait stand out vividly. The result is hopefully to indicate the following two points. First, the con-man theme is not restricted to Melville's or Twain's literary world, set in the Mississippi area, but extended to James's, set in the East and Europe. Second, in the Jamesian con game, played with the differences between the new and the old cultures for the background, the complexity of character and the center-of-consciousness technique play important parts, because the complexity convincingly proves the inevitability of the con game and the technique makes the con game full of suspense.