The number eight bus towards Telford was damaged in the attack, near the Silkin Way in Madeley at 8pm on Wednesday, when youngsters on a bridge threw a rock at the windscreen.
Two other buses were also targeted on the same evening.
Bosses at Arriva Midlands West are looking into the damage caused and say they won't hesitate to prosecute if they can find out who is responsible. The incident is one of a number of similar ones involving vehicles where rocks or stones have been launched at windscreens.
Chris Harvey, who drives for Arriva and is also a supervisor, posted a picture of the rock that caused the damage and said: "If anyone has any information this is one of the rocks involved in comparison to my hand before some of you think it's a pebble or a small stone.
To put this into perspective that rock, on the opposite side of the window could have injured or killed anyone on board instantly.
"We've already assessed one piece of damage at over £1,000 and if caught/charged we will want to prosecute.
A spokesman for West Mercia Police said: "This incident was reported to us along with a number of others which included damage to three buses. We are looking into it and other similar reports of damage from objects being thrown at vehicles."
Staffordshire Police recently said a series of incidents had been reported where bricks, rocks and other objects have been dropped onto passing cars on the M6 Toll Road, causing damage.