Pd (NH₃) ₄ [B (C₆H₅) ₄] ₂ was found to have photothermographic property. Its application to photographic system was studied by measuring the photographic sensitivity, the spectral sensitivity and the amplification factor and activation energy of thermal development. It was shown that this compound had fairly large photosensitivity in the wavelength range between 210 and 350 nm. The photographic sensitivity represented as the light energy required to produce D =0.1 above fog is 3×10⁵ erg/cm² at 310 nm. The thermal developability is nearly half as large as those of dioxalatopalladium salt and oxalatodiaminopalladium studied in our previous paper, with an amplification factor of 30. This compound is fairly stable while kept in the dark at room temperature, as compared with other palladium compounds such as cited above.