Disclosed is an electrocardiograph and a method for controlling the electrocardiograph having a function that reduces a burden on medical stuffs who are involved in an electrocardiogram test and evaluation for evaluating the possibility of ACS. The electrocardiograph automatically applies analysis processing to an electrocardiogram while continuously obtaining an electrocardiogram of the subject and displaying the electrocardiogram. The electrocardiograph executes an enhanced test that includes periodical execution of an electrocardiogram test, if the information obtained through the analysis processing satisfies the condition regarding the possibility of acute coronary syndromes (ACS).