A method of producing lipids, containing the steps of: culturing a transformant wherein a gene encoding the following protein (A) or (B), and a gene encoding the following protein (C) or (D) are introduced into a host cell, and producing medium-chain fatty acids or the lipids containing the same as components:
(A) a protein consisting of the amino acid sequence set forth in SEQ ID NO: 2;
(B) a protein consisting of an amino acid sequence having 60% or more identity with the amino acid sequence set forth in SEQ ID NO: 2, and having acyl-ACP thioesterase activity;
(C) a protein consisting of the amino acid sequence set forth in SEQ ID NO: 4; and
(D) a protein consisting of an amino acid sequence having 60% or more identity with the amino acid sequence set forth in SEQ ID NO: 4, and having β-ketoacyl-ACP reductase activity.