NIRS-KIT is a MATLAB-based cross-platform toolbox for both task and resting-state fNIRS data analysis with a user-friendly GUI. This toolbox covers the entire data analysis pipeline with batch processing, including raw data format conversion, data preview and quality check, preprocessing, individual-level analysis, group-level statistics and result visualization. For task fNIRS data analysis, individual-level statistical analysis is carried out to detect task-related neural activation based on the General Linear Model (GLM). For resting-state fNIRS data analysis, individual-level functional connectivity (FC), amplitude low-frequency fluctuation (ALFF), fractional ALFF can be calculated. In addition, NIRS-KIT can also perform the network metrics analysis by calling Gretna (Wang et al., 2015). For group-level analysis, NIRS-KIT provides several popular parametric models and multiple comparison correction approaches. NIRS-KIT provides both 2D and 3D visualization functions to visualize the statistical results.