The invention discloses a rock and soil mass grouting effect detecting device and method. The rock and soil mass grouting effect detecting device comprises a detector string. The detector string comprises a plurality of detector units. Each detector unit comprises a cylindrical shell, wherein a detector is arranged in the shell. The detectors of the multiple detector units are sequentially connected through a first cable. The shells of the multiple detector units are sequentially connected through a connecting rope. Each detector unit is further provided with a positioning mechanism and a contraction mechanism. The rock and soil mass grouting effect detecting method comprises the following steps that detection hole ways are arranged, and electric spark vibration sources and detector strings are placed in the different detection hole ways and are connected with a detection analysis system; a two-dimensional CT image is constructed through the computer inversion technology, two-dimensional CT images of a rock and soil mass before grouting and after grouting are compared, and the grouting area and the grouting effect are judged. The rock and soil mass grouting effect detecting deviceand method have the beneficial effects of being efficient, accurate, economical, visual and convenient to conduct.