This paper examines λ/4 type wave absorber using priodically-arranged short carbon fibers whose length is λ/2 or λ/4 for two arbitrary frequencies. The measurement result of wave absorber shows wideband absorption characteristics of around 20dB from 4 to 7GHz, and the thickness of the absorber is 34% thinner than a traditional λ/4 type wave absorber at 4.5GHz. Next, we performed for an estimate of the surface resistance of the aspect arranged short carbon fibers to enable the theoretical design of the absorber, and an estimate of the aspect confirmed what was performed precisely by the agreement of calculated and measured absorption characteristics of wave absorber. Then, we changed the thickness and materials of the spacer, and calculated absorption characteristics with estimated surface impedance. The spacer was thinner, absorption characteristics was wider than measured one by calculation. As a result, we showed that a design of wave absorber using periodically arranged short carbon fibers was theoretically possible.