A vital signs detecting device and a method for detecting vital signs are provided. The vital signs detecting device comprises a detection unit； a multimode optical fiber configured to be connected to a light source and to the detection unit； a mechanical structure configured for receiving a pressure exerted by a person's body as a result of one or more of a group consisting of a movement of the person's body, a respiratory action of the person's body and a heart beat action of the person's body and to cause microbending of the multimode optical fiber under the exerted pressure and； wherein the multimode optical fiber is disposed between first and second sets of microbending elements of the mechanical structure substantially in a direction of the exerted pressure.
