a process for producing a coumarin derivative represented by formula : ## str1 ## wherein r 1 to r 4 are as defined in the specification , comprising the step of : subjecting to a ring formation and dehydrogenation reaction a 3 -- propionic acid ester derivative represented by formula : ## str2 ## wherein r 1 to r 4 are as defined in the specification , the ring formation and dehydrogenation reaction being conducted by use of a catalyst comprising a carrier having supported thereon palladium and either of chromium oxide and chromium hydroxide , or conducted by use of a catalyst comprising a carrier having supported thereon palladium or a catalyst comprising a carrier having supported thereon palladium and either of chromium oxide and chromium hydroxide , in the presence of a promoter which is at least one member selected from the group consisting of magnesium trisilicate , zirconia , metallic chromium , and metallic tungsten .