In a mood analysis method using an electrocardiogram of a user, RR intervals in the electrocardiogram are computed, and low-frequency (LF) values and high-frequency (HF) values are also computed according to the RR intervals. Standard values of sympathetic nervous system (SNS) activity and parasympathetic nervous system (PSNS) activity are acquired corresponding to age and sex data of the user, to establish a mood display coordinate system. Coordinates of the LF values and the HF values in the mood display coordinate system are computed to determine a mood of the user.