A communication device for handling a cell selection procedure or a cell reselection procedure, regarding a plurality of beams belonging to a cell, the communication device comprising: a storage device; and a processing circuit, coupled to the storage device, wherein the storage device stores, and the processing circuit is configured to execute, instructions of: measuring a plurality of power values corresponding to the plurality of beams of the cell; determining a first quality value of the cell according to an average of the plurality of power values; determining an offset value according to a number of the plurality of beams corresponding to the plurality of power values; determining that the offset value is a first value, if the number of the plurality of beams is smaller than or equal to a first number; determining that the offset value is a second value smaller than the first value, if the number of the plurality of beams is greater than the first number; determining a second quality value of the cell according to the first quality value of the cell and the offset value; and performing the cell selection procedure to select the cell when the second quality value of the cell is greater than a first threshold or the cell reselection procedure to reselect the cell when the second quality value of the cell is greater than a second threshold. a storage device; and a processing circuit, coupled to the storage device, wherein the storage device stores, and the processing circuit is configured to execute, instructions of: measuring a plurality of power values corresponding to the plurality of beams of the cell; determining a first quality value of the cell according to an average of the plurality of power values; determining an offset value according to a number of the plurality of beams corresponding to the plurality of power values; determining that the offset value is a first value, if the number of the plurality of beams is smaller than or equal to a first number; determining that the offset value is a second value smaller than the first value, if the number of the plurality of beams is greater than the first number; determining a second quality value of the cell according to the first quality value of the cell and the offset value; and performing the cell selection procedure to select the cell when the second quality value of the cell is greater than a first threshold or the cell reselection procedure to reselect the cell when the second quality value of the cell is greater than a second threshold. measuring a plurality of power values corresponding to the plurality of beams of the cell; determining a first quality value of the cell according to an average of the plurality of power values; determining an offset value according to a number of the plurality of beams corresponding to the plurality of power values; determining that the offset value is a first value, if the number of the plurality of beams is smaller than or equal to a first number; determining that the offset value is a second value smaller than the first value, if the number of the plurality of beams is greater than the first number; determining a second quality value of the cell according to the first quality value of the cell and the offset value; and performing the cell selection procedure to select the cell when the second quality value of the cell is greater than a first threshold or the cell reselection procedure to reselect the cell when the second quality value of the cell is greater than a second threshold.