The present invention relates to a protective block which protects street trees in a road, a sidewalk, a part, a square, and a trail where trees are planted, and more specifically to a street tree protective block capable of shifting the center thereof, and adjusting an inner diameter thereof, comprising: inner blocks including an inner surface for forming a space unit in which a street tree is planted, and an outer surface formed in a waveform shape； and outer blocks connected to the outer surface of the inner block to be adjacent, having an internal surface having increased coupling force by having a waveform corresponding to a waveform of the outer surface of the inner block, and having an external surface bent in a right angle or a circular shape. The inner blocks are formed with four thereof, and side surfaces are adjacent and assembled with each other. The outer blocks are adjacent to the outer surface of the assembled inner block, and formed with four thereof. An adjacent surface between the assembled inner blocks and an adjacent surface between the assembled outer blocks are assembled not to be in contact with each other. According to the present invention, the center is assembled to be deflected to four inner blocks which are assemblies having different sizes of forming the space unit in which the street tree is planted, to flexibly move the space unit in accordance with a planting position of the street tree. Also, an inner diameter can be changed by adjusting the same to correspond to the thickness of the street tree by varying a combination of the inner blocks or installing only outer blocks without the inner blocks. The sagging and corrosion of a tree support stand can be prevented by a support stand groove capable of holding the tree support stand for supporting the street tree.본 발명은 수목이 식재되는 도로, 인도, 공원, 광장 및 산책로에서 가로수를 보호하는 보호블록으로, 보다 상세하게는 가로수가 식재될 공간부를 형성하는 내부면과, 파형으로 형성된 외부면을 이루는 내측블록 및 상기 내측블록의 외부면과 연접하여 결합되는 것으로 내측블록의 외부면의 파형과 대응되는 파형을 이루어 결합력을 높
