To investigate the microscopic magnetic nature of phospho-olivines, we have measured positive muon-spin rotation and relaxation (μ+SR) spectra for NaxFePO4 and FePO4, using powder samples in the temperature range between 2 and 200 K. For Na0.7FePO4, μ+SR measurements under zero external field (ZF) showed the appearance of static magnetic order below TN ∼ 61 K, at which the susceptibility χ(T ) exhibits a sharp maximum due to an antiferromagnetic (AF) transition. The wide distribution found for the internal magnetic field (Hint) was reasonably explained by the formation of AF order with the spread in Hint due to a random distribution of Na vacancies. On the other hand, the ZF spectra for FePO4 suggested the formation of the canted AF order below TN = 113 K, as proposed by neutron diffraction (ND), but the ratio between the y and x components of the ordered moment (My/Mx ) was determined as 0.6 by μ+SR, whereas 0.22 was measured by ND, probably indicating anisotropic spin fluctuations in FePO4.