Lattice stick number sL(K) is defined to be the minimal number of sticks required to construct a polygonal representation of the knot K in the cubic lattice. In this paper, we give lattice stick numbers of small knots such as 31 and 41. More precisely we prove that sL(31) = 12 and sL(K) ≥ 14 for any other non-trivial knot K.