We consider a first-passage percolation problem on the square lattice, where the distribution function of time coordinates of horizontal edges may be different from that of vertical edges. Some basic limit theorems for first-passage times and minimal lengths of optimal paths are obtained. Especially, we show that as long as the system is in the supercritical phase, the expectation of first-passage time from the origin to a point with distance $n$ converges to a finite constant, which is independent of the directions, as $n \to \infty$.