A variety of Josephson-junction-based qubits have recently been implemented with remarkable progress in coherence time and read-out scheme. These developments, together with its potential scalability, have renewed the position of this solid-state device as a strong candidate as a building block for the quantum computer. On the other hand, coupling multiple qubits to construct a logic gate is another important step toward the realization of quantum computer. In this paper, we present our experiments on conditional gate operations using coupled superconducting charge qubits.