A voltage adjusting method, a memory controlling circuit unit and a memory storage device are provided. The method includes: reading a first physical programming unit in a first physical programming unit group to obtain first data; correcting the first data according to a first error check and correction code corresponding to the first data to obtain first corrected data; reading a second physical programming unit in the first physical programming unit group to obtain second data; and adjusting a first read voltage for reading a first memory cell to a second read voltage according to the first data, the first corrected data, and the second data.