The present invention provides a method and an index capable of less-invasively determining myocardial ischemia such as ischemic heart disease or restenosis after percutaneous coronary intervention. The present invention also provides an index that allows the cardiovascular disease other than heart failure to be determined even from a blood sample showing a BNP value from which the cardiovascular disease other than heart failure cannot be determined by a conventional method. A method for determining myocardial ischemia comprising subjecting a blood sample which is derived from a test subject and which contains a BNP molecular group containing at least two selected from the group consisting of BNP 1-32 molecule, BNP 3-32 molecule, BNP 4-32 molecule, BNP 5-32 molecule, and a molecule having a mass number larger than that of BNP 5-32 molecule by 16 Da to a detection process capable of distinguishing and quantifying the individual BNP molecules different in mass number to detect the BNP molecular group, wherein myocardial ischemia in the test subject is determined using, as an index, a ratio between a detected intensity of at least one molecule selected from the BNP molecular group and a detected intensity of at least one other molecule selected from the BNP molecular group.