ALMA has been carrying out a monitoring program for calibrators since its beginning of science operations in 2011. The program covers 46 flux calibrators at Band 3 and Band 7 (or Band 6, complementary) with a cadence of ~10 days. Every observation is performed with a full polarization mode that allows us to measure Stokes parameters. Polarization properties of these calibrators are used for calibration procedure in PI-science polarimetry projects. Using polarized calibrator sources on the sky as a solution to characterize instrumental polarization corrections, we can perform polarization calibration without specific devices installed on the array. Therefore, monitoring Stokes parameters of these calibrators is essential for the ALMA polarization capability. Furthermore, the program reveals time variability of mm/sub-mm polarization that responds to the magnetic fields of AGN jets. In this poster, we present the performance of the polarization monitoring and explain how it works.