Two-dimensional faceted crystal growth of silicon from undercooled melt of Si-20 mass%Ni alloy was experimentally investigated, in which a droplet sample from 10 to 100 mg was undercooled on a single-crystal sapphire and growing crystals were observed in situ. Observed crystals were classified according to the shapes of square, wedge and irregular shapes. The growth velocity was measured for different undercooling conditions. The growth velocity of square shaped crystals was about half times smaller than that of wedge shaped crystals. The growth of square shaped crystals is regarded to be two-dimensional and it is compared with the results of two-dimensional phase-field simulations. Growth velocity in both is in good agreement and the linear kinetic coefficient is estimated to be 0.002 m/sK.