The invention relates to a sludge drying device, which is suitable for a sludge drying process before thermal power burning. The device consists of a sludge storage pool used for storing sludge, a sludge concentrator used for primarily concentrating the sludge, a chemical adding device used for adding a flocculant into the sludge concentrator, a concentrated sludge tank for storing primarily concentrated sludge, a transforming kettle for the reaction of the primarily concentrated sludge, a transforming agent, a stabilizing agent and a deodorant, a preparing kettle for preparing the transforming agent, the stabilizing agent and the deodorant, a filter press used for removing sludge moisture in the transforming kettle, a crushing device used for crushing dried sludge, and an absorption tower for absorbing odor generated in the drying process. The sludge drying device disclosed by the invention has the advantages of high dehydration efficiency, energy saving, environmental protection, good drying effect and cost saving.