Photothermographic properties of several metal oxalates and complex oxalates were studied by measuring the reflection density of irradiated and then heated plates on which studied materials were coated. Potassium dioxalatocuprate (II) and oxalatodiaminopalladium (II) were newly found to be photothermographic. Oxalatodiaminopalladium (II) is photosensitive at 300 to 400 nm. Evolution of ammonia gas from this complex was detected while it photodecomposed. It is assumed that photolysis and thermal decomposition of the complex proceeds as follows: Pd (NH₃) ₂C₂O₄→Pd+2NH₃+2CO₂ Ferric oxalate is sensitive to the light at 250 to 500 nm. This salt is sensitive to both light and heat, but shows no photothermographic property. From these results it is suggested that the palladium (II) complex is applicable for image forming.