To provide a panel for a building and its manufacturing method causing no crack in mortar even if years pass, and easily constructing a wall of the building by integrating felt and a lath net.

Projecting parts 22 having a through hole 21 in a surface of a plate 10 are arranged in large numbers in a multi-line and multi-row. Opening holes 23 and 23 are arranged on both sides of the projecting parts 22 so as to continue with the through hole 21. A projecting piece 24 for blocking up the respective opening holes 23 in a half opening state projects to the reverse side of the plate 10. Recess-projection parts 20 composed of the through hole 21, the projecting parts 22, the opening holes 23 and a projecting piece 24 are arranged in a multi-line and multi-row in a state of aligning in the same direction. Groove-shaped ribs 11 recessed to the reverse side of the plate 10 are also arranged in a plurality in a stripe shape. The recess-projection parts 20 are arranged in a part for arranging no these ribs 11.