To improve the technique of a beginner in such a manner that a theoretical target point in order to let a targeted ball run just like an image in a pocket billiards is concretely shown, and a practice to accurately shoot a cue ball is repeated.

A protuberance 4 is provided on the outer peripheral section of a disk 3, wherein a circle 1 having the same diameter as the ball used for the game and the central point 2 are clearly shown, is provided. A length 6 from the central point 2 to the tip end 5 of the protuberance 4 is determined in such a manner that the tip end of the protuberance is adjusted to a ground-touching point 10 of the targeted ball, while a central line 7 connecting both parts may be superposed with a line 9 along which the targeted ball 8 in needed to run. Then, when the disk 3 is set on a table 11 with the ground-touching point 10 as a starting point, the circle listed on the disk 3 and the central point 2 are made to indicate a flat surface location of a ball imaged at a location coming exactly into contact with the targeted ball 8 (= image ball) and the central point 2 (= imaginary point). In this case, the setting is facilitated when a pair of guides 27 are provided ahead from both sides of the tip end of the protuberance 4, and the ground-touching point 10 of the targeted ball 8 is pinched by both guides 27.