Hot bands of the SiF radical were investigated by infrared diode laser spectroscopy. Numerous transitions belonging to the bands ν = 1-0 through 9-8 for both 2 Π 1 2 and 2 Π 3 2 were observed by the use of glow discharge in SiF 4 diluted with a large amount of Ar. The observed transition wavenumbers were subjected to a least-squares analysis, by using a newly derived effective Hamiltonian represented as a matrix whose elements are operators in the space of the internuclear distance r. Precise potential function and the r-dependence of the spin-orbit coupling constant are presented graphically as well as in the polynomial expansion. The equilibrium rotational constant and harmonic vibrational frequency are B e = 0.581 257 45 ± 0.000 000 60 and ω e = 857.3254 ± 0.0011 cm - 1 , respectively, where the uncertainties correspond to three standard deviations. The equilibrium bond length is derived as r e = 1.600 996 5 ± 0.000 002 1 9.