The object of the present invention is to improve the dissolution and the absorption of (S)-1-(3-(4-amino-3-((3,5-dimethoxyphenyl)ethynyl-1H-pyrazolo[3,4-d]pyrimidin-1-yl-1-pyrrolidinyl)-2-propen-1-one effective as an antitumor agent from a pharmaceutical formulation comprising the same. Provided is a pharmaceutical composition comprising (S)-1-(3-(4-amino-3-((3,5-dimethoxyphenyl)ethynyl-1H-pyrazolo[3,4-d]pyrimidin-1-yl-1-pyrrolidinyl)-2-propen-1-one in combination with sodium alkyl sulfate having an alkyl group containing 10 to 18 carbon atoms, in particular, with sodium lauryl sulfate.