In the past two decades, one of the fascinating subjects in quantum physics has been quantum bits (qubits). Thanks to the superposition principle, the qubits can perform many calculationssimultaneously, which will significantly increase the speed and capacity of the calculations. The time when a qubit lives in an excited state is called decoherence time. The decoherence time varies considerably depending on the qubit type and materials. Today, short decoherence times are one of the bottlenecks in implementing quantum computers based on superconducting qubits. In this research, the topology of the transmon qubit is investigated, and the decoherence time caused by noise, flux, and critical current noise is calculated by numerical method.