Electromagnetic scattering from multiple slits in a thick, perfectly conducting plane is investigated. The Fourier transform and mode matching are used to obtain the simultaneous equations. The simultaneous equations are solved to obtain a series solution which reduces to a closed form in the high-frequency limit. The transmission coefficients are represented in fast convergent series which are efficient for numerical computations. Numerical computations are performed to illustrate their scattering behaviors in terms of frequency, slit size, and slit number.