PURPOSE: A simultaneous assay method of multiplex cytochrome P450 enzyme activity is provided to simultaneously measure the activity change of various cytochrome P450 enzymes and to study diseases related to the cytochrome P450 enzyme activity. CONSTITUTION: A simultaneous assay method of multiplex cytochrome P450 enzyme activity comprises: a step of simultaneously extracting steroid hormone metabolic products including male hormones, female hormones, corpus luteum hormones, sterol, and adrenal cortical hormones from urine; a step of re-extracting the extracts using an organic solvent and performing trimethyl silyl derivatization; and a step of measuring the concentration of steroid hormone biometabolic products in the urine by gas chromatography-mass spectrometer. [Reference numerals] (AA) Before dosing a drug; (BB) After dosing a drug;
