No. It's not if you Itemized on this year 2018. It's on your 2017 return.
A State Tax Refund is taxable if you itemized deductions on that prior year's federal return and took a deduction for state income taxes instead of the sale tax. You got a deduction benefit for it so now you have to include it as income. If you took the standard deduction or filed a 1040EZ or 1040A it is not taxable and you don't need to report it.
See 2017 Schedule A
https://www.irs.gov/pub/irs-prior/f1040sa--2017.pdf
