Metal sheet material, layered body, insulated circuit board, and metal sheet material manufacturing method

A metal sheet material made of copper or a copper alloy, comprising:

• a main sheet body;
• and
• a roughened plating layer that is formed on an outermost surface layer of the main sheet body,
• wherein an engagement protrusion that protrudes toward an opposite side to the main sheet body and has a widening portion that gradually widens in width toward a tip end side in a protrusion direction is formed in the roughened plating layer,
• in a cross section of the main sheet body along a thickness direction, a plurality of the engagement protrusions are formed on a surface crystal grain that is located on the outermost surface of the main sheet body, and
• when a maximum width of the surface crystal grain is denoted by W (unit:
• μm), a number of the engagement protrusions in the maximum width of the surface crystal grain is denoted by N, and a protrusion height of the engagement protrusions is denoted by H (unit:
• μm), N×H/W is 0.5 or greater.