A carbon dioxide gas absorbent includes a porous body containing a lithium
complex oxide. The porous body includes pores having a pore diameter
distribution such that main pores which consist of first pores with a
diameter of 10 to 100 .mu.m and second pores with a diameter larger than
100 .mu.m and 500 .mu.m or smaller occupy 80 to 100%, third pores with a
diameter smaller than 10 .mu.m occupy 0 to 10% and fourth pores with a
diameter larger than 500 .mu.m occupy 0 to 10%, the main pores have a
pore diameter distribution such that the first pores occupy 15 to 85% and
second pores occupy 15 to 85%.