A-site-ordered perovskites La1-xNaxMn3Ti4O12 with (x = 0, 0.5, 1) were synthesized under high-pressure and high-temperature conditions, and their crystal structures and magnetic properties were investigated. Ti/Mn occupancies at the B site were also examined by using resonant X-ray diffraction, and the results confirm that they are stoichiometric with high Ti/Mn site selectivity. Substitution of Na+ for some of the La3+ changes the valence state of the A'-site Mn but not of the B-site Ti, and thus the compositions of the synthesized samples are expressed as La1-xNaxMn3{(5+2x)/3}+Ti44+O12. The magnetic properties change from spin-glass-like to antiferromagnetic to spin-glass-like behavior according to the valence states of A'-site Mn.