An ultrasound observation apparatus includes: a main power-supply button that operates an internal power-supply unit to be turned on/off as a result of depression of the main power-supply button； a moving member capable of moving substantially in parallel to a direction of the depression of the main power-supply button in conjunction with the depression of the main power-supply button； an internal power-supply switch provided at the power-supply unit so as to be in contact with the moving member, the internal power-supply switch switching the power-supply unit on/off by being depressed along with movement of the moving member； and a movement amount adjusting mechanism that upon the depression of the main power-supply button, if an amount of movement of the main power-supply button exceeds a predetermined movement amount, adjusts an amount of movement of a contact portion of the moving member.
