An increasing number of individuals in aging populations are affected by urination disorders such as benign prostatic hyperplasia and overactive bladder. Bladder diaries are widely used in the diagnosis of these disorders. Patients record the time of urination and voided volume (VV) for 3 consecutive days in their bladder diaries. A urine collection container is required for VV measurement. Inappropriate disposal or cleaning of instruments after use can result in the transmission of infection. In addition, self-recording of bladder diaries often have problems such as inaccurate recording or missing entries of urinary output. To address these issues, we developed a water-soluble paper urine collection container that can be flushed down the toilet. This system was also developed to measure VV and urinary flow rate parameters. VV, maximum urinary flow rate (Qmax), and average flow rate (Qave) were estimated based on the increase in capacitance between the electrodes placed on the exterior of the container. In a basic experiment, 0.9% saline solution was used as pseudo-urine. The relationship between the volume of pseudo-urine and change in capacitance (Δx) exhibited a strong linear correlation (R² > 0.99). A correction factor (k ≈ 1.31) was applied to account for the difference in dielectric constant between urine and saline solution. The conversion from Δx to VV was determined based on the results of the basic experiment. In a urination measurement experiment, five young males (23 ± 1 years) without symptoms of urination disorders participated. Each subject urinated ten times. Simultaneous measurements were obtained using the proposed system and a medical uroflowmeter (PicoFlow2, MEDICA S.p.A., MO, Italy). The mean errors (mean ± SD) for VV, Qmax, and Qave were 14.9 ± 41.8 mL, 2.5 ± 6.0 mL/s, and 2.0 ± 2.6 mL/s, respectively. The mean absolute percent error for VV, Qmax, and Qave were 14.1%, 15.9% and 19.9%, respectively. Paired t-tests (significance level, p < 0.01) showed no significant differences between the two measurement methods for any of the parameters. Bland-Altman analysis revealed no systematic error between the proposed system and the medical uroflowmeter for any of the items. The VV, Qmax, Qave measured using the proposed system agree well with those measured using a medical uroflowmeter. This system can be expected to be a hygienic and portable uroflowmeter that can contribute to automated bladder diary recording.