According to Steel's office, the rock was thrown through the second-story window of the office in the 10800 block of Holder Street on Friday morning.
No injuries were reported. She shared several photos of the damage, two of which show the shattered window.
"Violence of any kind has no place in our society, and no amount of it will stop me from doing what I believe is right for Southern California families,'' said Steel, R-Cypress, in a statement.
The attack was the second instance of vandalism at the office this year, according to a statement from Steel's representatives, who blamed pro-Palestinian protesters for damage caused in January.
There was no indication of who carried out the rock-throwing attack Friday.
According to her office, it occurred "after Steel's office received dozens of calls from pro-Hamas protesters demanding she not attend (Israeli Prime Minister) Benjamin Netanyahu's address to Congress."
The incident is being investigated by the Cypress Police Department.
City News Service, Inc. contributed to this report.