In order to study the variation of a microscopic internal magnetic field with the Ca content $(x)$, we have systematically measured muon-spin rotation and relaxation $({\ensuremath{\mu}}^{+}\mathrm{SR})$ spectra for ${\mathrm{Sr}}_{1\ensuremath{-}x}{\mathrm{Ca}}_{x}{\mathrm{Co}}_{2}{\mathrm{P}}_{2} (0\ensuremath{\le}x\ensuremath{\le}1)$ powder samples mainly in a zero external field. As $x$ increases from 0, a Pauli-paramagnetic phase is observed even at the lowest $T$ measured (1.8 K) until $x=0.45$; then, a short-range antiferromagnetic (AF) ordered phase appears for $0.48\ensuremath{\le}x\ensuremath{\le}0.75$, and finally a long-range AF ordered phase is stabilized for $x\ensuremath{\ge}0.75$. The evolution of the magnetic order is connected to the shrinking of the $c$-axis length as a function of $x$, which naturally enhances the AF interaction between the two adjacent Co planes.