The authors have developed a method to reconstruct the 3D dose distribution in a particle beam scanning irradiation system. In this scheme, 3D dose distribution is reconstructed by using the measured images of fluence distribution, which are taken for each iso-energy slice (i.e., the unit of the depth scanning). A fluorescent screen with a CCD camera is used to measure the fluence distribution. This system was installed at the HIMAC experimental port and tested by using carbon ion beams. Since a maximum difference between the reconstructed dose and the ionization chamber measurement was around 5% in the target volume, this system can be useful for quick verification of 3D dose distribution.