Hello:

My question is about linear reg. analysis with stepwise in SPSS.

In output:

In Coefficients estimate table:

there are parameters in Unstandardized Coeff. (B) part and Standardized
Coeff. Part (Beta).

When we write the reg. equation, which one goes to equation as a
parameter?

You probably want to use B.

B is the coefficient of proportionality (i.e. the slope of the line) between the dependent variable and the independent variable. In other words, it determines how many units the dependent variable would increase or decrease for a one-unit increase in the independent variable.

Beta is also a coefficient of proportionality, but it's scaled to determine how many standard deviations the dependent variable changes for a one-standard-deviation increase in the independent variable. It's a very useful measure because it gives you an idea of how sensitive the correlation is, regardless of scale.

But as I said at the beginning, if your goal is to simply write out the equation of the line of best fit, B is the variable you want to use.

This page talks about this topic:
How to Use SPSS 7.