  We demonstrate electron spin polarization detection and electron paramagnetic
resonance (EPR) spectroscopy using a direct current superconducting quantum
interference device (dc-SQUID) magnetometer. Our target electron spin ensemble
is directly glued on the dc-SQUID magnetometer that detects electron spin
polarization induced by a external magnetic field or EPR in micrometer-sized
area. The minimum distinguishable number of polarized spins and sensing volume
of the electron spin polarization detection and the EPR spectroscopy are
estimated to be $\sim$$10^6$ and $\sim$$10^{-10}$ $\mathrm{cm}^{3}$ ($\sim$0.1
pl), respectively.
