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 and the roughened plating layer 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, when an interface between the main sheet body and the roughened plating layer, which is observed in the cross section of the main sheet body and the roughened plating layer along the thickness direction, is observed with a scanning electron microscope at a 1000-fold magnification, a measurement of a maximum width of the surface crystal grain in a field of view of 85 μm×120 μm is performed three times, and the maximum width of the surface crystal grain denoted by W (unit:
• μm) is defined as a maximum value among three measurements, the maximum width of the surface crystal grain is 3 μm or greater and 1000 μm or less, and when 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), wherein N×H/W is 1.11 or smaller.