Fusarium heterosporum lipase is composed of an N-terminal large peptide of 275 amino acids and a C-terminal peptide of 26 amino acids. The thermostability of the lipase was remarkably decreased by cleavage of the C-terminal peptide. Hence, we attempted to specify the amino acids in the C-terminal peptide that are responsible for the stabilization of the lipase. Replacement of Asp293 with Ale, Asn, and Lys caused a significant decrease in thermostability, but its mutation to Glu did not decrease the stability significantly. These Endings showed that the lipase with the C-terminal peptide was stabilized by an ionic bond between the negative charge of Asp293 and positive charge of an amino acid of the N-terminal large peptide. The thermostability of the lipase gradually decreased with increasing deletion size from the C-terminus, and a 13-amino acid deletion decreased the stability to the level of the lipase not having the C-terminal peptide. These results suggested that the W-amino acid region from the C-terminus participated in the lipase stability. In addition, the lipase production correlated well with the lipase stability, showing that the C-terminal peptide also influenced the lipase productivity.