A biometric apparatus comprising: a first detector configured to detect and output a brain activity signal indicating a state of brain activity in a target person; and a signal processing circuit, wherein the signal processing circuit is configured to: - acquire the brain activity signal, - acquire a biological signal of the target person that is different from the brain activity signal, - determine, based on the biological signal and the brain activity signal a state of the target person, and - generate and output a signal indicating the state of the target person; wherein the brain activity signal includes information on a change in a quantity of cerebral blood flow in the target person; and the signal processing circuit is configured to: - determine, based on the biological signal, whether the biological signal is within a standard range; - determine, based on the brain activity signal, whether an amount of change in the cerebral blood flow is smaller than a standard value; and - in response to the determination that the biological signal is within the standard range, determine that the state of the target person is a normal state; characterized in that: the signal processing circuit is configured to: - in response to the determination that the biological signal is not within the standard range and the determination that the amount of change in the cerebral blood flow is smaller than the standard value, determine that the state of the target person is a state of disturbed consciousness, the target person being unconscious during the state of disturbed consciousness; and - in response to the determination that the biological signal is not within the standard range and the determination that the amount of change in the cerebral blood flow is not smaller than the standard value, determine that the state of the target person is a sleeping state. a first detector configured to detect and output a brain activity signal indicating a state of brain activity in a target person; and a signal processing circuit, wherein the signal processing circuit is configured to: - acquire the brain activity signal, - acquire a biological signal of the target person that is different from the brain activity signal, - determine, based on the biological signal and the brain activity signal a state of the target person, and - generate and output a signal indicating the state of the target person; - acquire the brain activity signal, - acquire a biological signal of the target person that is different from the brain activity signal, - determine, based on the biological signal and the brain activity signal a state of the target person, and - generate and output a signal indicating the state of the target person; wherein the brain activity signal includes information on a change in a quantity of cerebral blood flow in the target person; and the signal processing circuit is configured to: - determine, based on the biological signal, whether the biological signal is within a standard range; - determine, based on the brain activity signal, whether an amount of change in the cerebral blood flow is smaller than a standard value; and - in response to the determination that the biological signal is within the standard range, determine that the state of the target person is a normal state; - determine, based on the biological signal, whether the biological signal is within a standard range; - determine, based on the brain activity signal, whether an amount of change in the cerebral blood flow is smaller than a standard value; and - in response to the determination that the biological signal is within the standard range, determine that the state of the target person is a normal state; characterized in that: the signal processing circuit is configured to: - in response to the determination that the biological signal is not within the standard range and the determination that the amount of change in the cerebral blood flow is smaller than the standard value, determine that the state of the target person is a state of disturbed consciousness, the target person being unconscious during the state of disturbed consciousness; and - in response to the determination that the biological signal is not within the standard range and the determination that the amount of change in the cerebral blood flow is not smaller than the standard value, determine that the state of the target person is a sleeping state. - in response to the determination that the biological signal is not within the standard range and the determination that the amount of change in the cerebral blood flow is smaller than the standard value, determine that the state of the target person is a state of disturbed consciousness, the target person being unconscious during the state of disturbed consciousness; and - in response to the determination that the biological signal is not within the standard range and the determination that the amount of change in the cerebral blood flow is not smaller than the standard value, determine that the state of the target person is a sleeping state.