To provide a block structure which can prevent planar displacement and lift/sinking and which can prevent the overgrowth of weeds, and a block for use in the block structure.

In this block structure 10, the blocks 18-21 are arranged. In the blocks 18-21, first and second flange portions 12 and 13 and a first connecting portion 14 are protruded on the lower sides of lateral sides crossing each other at one corner A formed of diagonal lines of a rectangle in a plan view; and a third and a fourth flange portions 15 and 16 and a second connecting portion 17 are protruded on the upper sides of lateral sides crossing each other at the other corner. The third flange portion 15 of the block 19 covers the first flange portion 12 of the block 18; the fourth flange portion 16 of the block 20 covers the second flange portion 13 of the block 18; the third and fourth flange portions 15 and 16 of the block 21 cover the first flange portion 12 of the block 20 and the second flange portion 13 of the block 19; and the first and second flange portions 12 and 13 are provided with gap covering portions 22 and 23 for covering the first connecting portion 14, respectively.