A wearable device according to an embodiment comprises a body configured to surround the outside of a subject, a light emitting unit arranged on an inner periphery of the body and including at least one first light emitting element, a light-receiving unit arranged on the inner periphery of the body and arranged opposite the light emitting unit, a display unit arranged on an outer periphery of the body and including at least one second light emitting element, and a first flexible substrate mounted with the at least one first light emitting element and the at least one second light emitting element, and the first flexible substrate has a first surface and a second surface opposite to the first surface, and the at least one first light emitting element and the at least one second light emitting element are mounted on the first surface of the first flexible substrate.