We propose the simple new method for extracting the value of the black hole spin from the direct high-resolution image of black hole by using a thin accretion disk model .
In this model the observed dark region on the first image of the supermassive black hole in the galaxy M87 , obtained by the Event Horizon Telescope , is a silhouette of the black hole event horizon .
The outline of this silhouette is the equator of the event horizon sphere .
The dark silhouette of the black hole event horizon is placed within the expected position of the black hole shadow , which is not revealed on the first image .
We calculated numerically the relation between the observed position of the black hole silhouette and the brightest point in the thin accretion disk , depending on the black hole spin .
From this relation we derive the spin of the supermassive black hole M87* , a = 0.75 \pm 0.15 .