Deterioration of Reinforced Concrete (RC) structures is related to the corrosion of reinforcement since it propagates to structural degradation. In urban or underground conditions, carbonation-initiated corrosion in reinforcement is reported. In this paper, a stochastic model for predicting service life of RC structure subjected to carbonation is proposed through Monte Carlo simulation method with the spatial variation of material, geometric properties of RC structures, and environmental factors. This model can take into account the spatial variation of uncertain parameters by generating non-Gaussian and multi-dimensional random fields using spectral representation method. To estimate the temporal variation of the probability to exceed a pre-defined serviceability, time-dependent reliability analyses are performed. Spatial reliability indicators such as the mean and standard deviation of the area are calculated through 20-sample with 4-variable full-factorial realization. It is evaluated that there exists large variation in predicted service life and quality control for concrete is required during construction for the service life. Based on these results, design and construction considerations are provided.