The device for plastering of building surfaces and underfloor screed pouring is an original construction, consisting of a panel located on a bar reciprocally perpendicular to another, and interactive elements, efficient in the operative operations, for the plastering process, whereby the technical layer of plastering construction surfaces and underfloor screed pouring progress substantially, revealing a substantial increase in plaster quality, screed and expansion of technological possibilities. The use of the building surface plastering device and the casting of the underfloor screed, with regard to the technologies and means of plastering the construction surfaces and the casting of the underlying screed, allows the following: Reduce: - physical effort; - work up to 20 times; - execution time up to 20 times; - cost price of the plaster up to 3 times; - overhead costs. increases: - labor productivity up to 20 times; - substantially the quality of plaster and screed. improves: - working conditions; - work safety. It favors technological premises. E.g: - performing decorative plaster with ornaments of any model, including basoreliefat ; - execution of plaster at low temperatures; - rendering plaster with cheap and qualitative mortar, thus canceling the use of expensive mortar from dry mix; - renouncing expensive machinery and mechanisms involved in the plastering process.