Yes, this is a balanced chemical equation, and it obeys the Law of Conservation of Mass.
A balanced chemical equation obeys the Law of Conservation of Mass if there are the same numbers of each type of atom on each side of the reaction arrow.
2H₂ + O₂ ⟶ 2H₂O
Let’s check the numbers.
Atom On the left On the right
H 4 4
O 2 2
We have the same numbers of H and O atoms on each side of the reaction arrow.
The equation is balanced and it obeys the Law of Conservation of Mass.