Generally, increasing a monster's level does not automatically increase its attack.
However, some monsters have effects that specifically state that their attack increases based on their level. These effects are unique to each card and you will need to check the card text for specific information.
Here are some examples:
* "Level Up!" monsters: These monsters have effects that allow them to increase their level during the duel, and often their attack will increase as well.
* "Rank-Up" monsters: These monsters can be summoned by using existing monsters on the field, and their attack will often increase based on the level of the monsters used to summon them.
* "XYZ monsters": These monsters are summoned using other monsters on the field, and their attack is usually determined by the combined level of the monsters used to summon them.
It's important to remember that each card has its own unique effects. Be sure to read the card text carefully to understand how each monster functions.