This biometric information detection device includes: a sensor including a light emitting element that is able to emit light and a light receiving element that is able to receive the light emitted from the light emitting element; a sealing member which includes a first light-transmitting part that covers the light emitting element and is able to transmit the light and a second light-transmitting part that covers the light receiving element and is able to transmit the light, and seals the sensor; and a holding member that is attached to at least one of the teeth and the gums and is able to hold the sealing member.