The marine sedimentary cores were measured by using imaging plate (IP), which is a 2-D radiation detector and has high-resolution, high-sensitivity and detectability of several type of radiation. The same cores were measured by two different devices to evaluate the measuring ability of IP, one is Natural Gamma Logger (NGL), which is a radiation detector in practical use, and another one is X-ray CT Scanner, whose unique value "CT Value" is considered to be proportional to density. Although characteristic dose distributions were found in the organism layer and the volcanic ash layer by using IP, they were not observed by NGL result. It means IP have enough resolution and sensitivity to comprehend the distribution of substances in the marine sediment. The dose distributions measured by using IP and CT Values showed good correlations. Taken into consideration the fact that CT Value is proportional to density, it could be said that doses tend to depend density in marine sediments. The high-dose point was found by using IP, but it was not observed by the results of NGL and X-ray CT scanner. It implies that IP could be a new nondestructive device to discover the target point.