A retaining device for a wood sawing machine contains an index table fixed on a cutting deck of the wood sawing machine to displace straightly and reciprocately along the cutting deck; a guiding plate fixed on the cutting deck, connected with the index table, and including a slot disposed thereon; a vertically moving set including at least one sliding block, at least one screw rod, a longitudinally displacing holder, at least one first adjusting nuts, and at least one first second adjusting nuts; wherein the sliding block is slidably connected with the slot of the guiding plate and displaces along the slot reciprocately, the screw rod is coupled on the sliding block respectively; a retaining and pressing assembly including a handle, two arms, two connecting posts, two stems, and a pressing panel.