The present invention relates to a stratum deformation monitoring device. The device includes a working tube having an outer surface and an in-tube space and buried into a target stratum; a plurality of deformation monitoring rings, each of which the plurality of deformation monitoring rings are movably assembled on the outer surface of the working tube in equal intervals or unequal intervals; and at least one strain optical fiber movably assembled on the outer surface of the working tube by securing on the plurality of deformation monitoring rings.