A foldable display device includes: a first substrate, a first thin-film transistor layer on the first substrate, a light emitting element layer on the first thin-film transistor layer, and a fingerprint sensor layer to receive light reflected by an external object. The fingerprint sensor layer includes: a second substrate under the first substrate, a second thin-film transistor layer under the second substrate, and a light receiving element layer under the second thin-film transistor layer.