The preset paper proposes a novel acoustic diffuser which we call cross rib diffuser (CRD) and investigates its acoustical performance in rooms experimentally. CRD consists of overlapping two one-dimensional periodic rib diffuser (OPRD) with different structural configurations. CRD can achieve high scattering coefficient with wider frequency band than OPRD. Moreover, unlike other diffusers with high scattering property such as metadiffuser and two-dimensional quadratic diffuser, CRD keeps simple and familiar design of OPRD suitable for use in various architectural spaces. In the paper, we firstly evaluated random-incidence scattering coefficient of CRD using 1/5 scaled reverberation room. Then, random-incidence absorption coefficient was measured in 1/1 reverberation room. Finally, an implementation experiment was conducted to examine applicability of CRD in improving acoustics in small meeting room with small absorption treatments. The results indicated that CRD reduced EDT and reverberation time, and increased D50 more than JND values. Additionally, CRD improved reverberation and speech intelligibility more significantly than OPRD with same installation area.