In order to objectively grasp a stress state of a user and to prevent postpartum depression, biological gas information is acquired via a network, where the biological gas information indicates a concentration of benzyl alcohol of the user and is obtained by a sensor that detects benzyl alcohol released from a skin surface of the user. From a memory storing information including an upper limit of a normal range of the concentration of benzyl alcohol per unit period, the information indicating the upper limit of the normal range is read out. When a frequency in the unit period with which the concentration of benzyl alcohol of the user exceeds the upper limit of the normal range is determined to have an increasing tendency based on the biological gas information obtained during a pregnancy period of the user, the information related to stress of the user is output to an information terminal of the user.
